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THE  EVOLUTION  OF  MAN 


Fig.  1.  Above,  skull  from  La  Chapelle-aux-Saints  represent- 
ing Neandertal  man.  Restored  by  McGregor.  R,  portion  re- 
stored. Below,  skull  from  Grotte  des  Enfants,  representing 
Cro-Magnon  man.  After  Verneau.  Reproduced  by  courtesy  of 
Professors  J.  H.  McGregor  and  W.  K.  Gregory. 


The  Evolution  of  Man 

^  Series  of  Lectures  T)elivered  before  the 

Yale  Chapter  of  the  Sigma  Xi  during  the 

Academic  Tear  1921-1922 

By 

Richard  Swann  Lull 

Harry  Burr  Ferris 

Qeorge  Howard  barker 

fames  Rowland  Angell 

<tAlbert  Galloway  Keller 

Sdwin  Qrant  Gonklin 

edited  by  Qeorge  Alfred  "Baitsell 


JP 


NEW  HAVEN 
YALE  UNIVERSITY  PRESS 

London  :  Humphrey  Mi  If  or  d  :  Oxford  University  "Press 
MDCCCCXXII 

\     • 


COPYRIGHT,   1922,   BY 
YALE    UNIVERSITY    PRESS 


First  published,  October,  1922 
Second  printing,  December,  1922 


]^-w(    Wa' 


PREFACE 

The  contents  of  this  book  have  as  their  basis  a  series  of  lec- 
tures bearing  the  same  title  which  were  given  at  Yale  Univer- 
sity, during  the  academic  year  1921-1922,  under  the  auspices  of 
the  Society  of  the  Sigma  Xi.  As  President  of  the  Yale  Chapter 
for  that  year  it  became  my  duty  to  arrange  the  program  for 
the  Society,  and  after  considerable  thought  I  came  to  the  con- 
clusion that  the  previous  successful  series  of  Sigma  Xi  lectures, 
which  were  given  in  1916-1917,  and  later  published  by  the 
Yale  University  Press,  on  "The  Evolution  of  the  Earth  and 
Its  Inhabitants,"  could  be  continued  with  interest  and  profit  by 
another  series  in  which  specific  consideration  was  given  to  the 
question  of  the  evolution  of  man.  Accordingly  a  series  of 
lectures  was  arranged  as  follows : 

THE  EVOLUTION  OF  MAN 

Lecture  I.  The  Antiquity  of  Man,  December  2,  192 1,  Pro- 
fessor Richard  Swann  Lull. 

Lecture  II.  The  Natural  History  of  Man,  January  20,  1922, 
Professor  Harry  Burr  Ferris. 

Lecture  III.  The  Evolution  of  the  Nervous  System  of  Man, 
February  10,  1922,  Professor  George  Howard  Parker. 

Lecture  IV.  The  Evolution  of  Intelligence,  April  11,  1922, 
President  James  Rowland  Angell. 

Lecture  V.  Societal  Evolution,  March  10,  1922,  Professor 
Albert  Galloway  Keller. 

Lecture  VI.  The  Trend  of  Evolution,  March  22,  1922, 
Professor  Edwin  Grant  Conklin. 

The  first  lecture,  by  Professor  Lull,  sets  forth  the  paleonto- 
logical  evidence  for  the  evolution  of  man.  In  the  second, 
Professor  Ferris  gives  in  detail,  largely  from  the  anatomi- 
cal  and  embryological  standpoints,   some   of  the   important 


vi  PREFACE 

evidence  for  evolution  which  Is  to  be  found  In  the  development 
and  structure  of  present-day  man.  The  third  and  fourth  lec- 
tures, by  Professor  Parker  and  President  Angell  respectively, 
constitute  a  unit  In  which  the  evolution  of  the  highly  special- 
ized and  preeminent  nervous  system  of  man  together  with  the 
development  of  Intelligence  are  given  consideration.  Pro- 
fessor Keller,  In  the  fifth  chapter,  presents  the  question  of  evo- 
lution In  the  various  institutions  of  human  society,  and,  finally. 
Professor  Conklin  sets  forth  his  views  with  regard  to  the  trend, 
or  future,  of  evolution.  The  large  attendance  at  each  of  the 
lectures  is  sufficient  evidence  of  the  extreme  interest  In  the 
question  of  the  evolution  of  man,  and  It  Is  hoped  that  the  pub- 
lication of  this  book  will  stimulate  an  even  greater  Interest 
in  this  very  important  subject.  It  is  believed  that  the  main 
scientific  facts  which  bear  upon  the  question  are  here  presented 
from  a  modern  viewpoint  in  an  interesting  as  well  as  authori- 
tative manner. 

In  conclusion,  as  President  of  the  Society  and  editor  of  this 
volume,  I  desire  to  express  my  deep  gratitude  to  the  authors 
for  their  willingness  to  take  the  time  and  energy  to  prepare  the 
lectures  and  to  arrange  their  manuscripts  for  publication;  to 
the  officers,  committees,  and  members  of  the  Yale  Chapter  of 
Sigma  Xi  who  by  their  enthusiastic  cooperation  made  It  pos- 
sible to  carry  through  the  year's  program  successfully;  to  my 
colleagues  in  the  Department  of  Zoology  and  elsewhere  in  the 
University,  who  have  shown  their  active  Interest  in  the  project 
in  many  ways,  and,  finally,  to  the  Yale  University  Press  for 
the  splendid  attitude  they  have  shown  in  all  matters  connected 
with  the  publication  of  this  volume. 

GEORGE  A.  BAITSELL, 

President,  Yale  Chapter,  Sigma  Xi, 

1921-1922. 
Oshorn  Zoological  Laboratory, 

Yale  University,  July,  ig22. 


CONTENTS 

PAGE 

Preface 

GEORGE   ALFRED    BAITSELL 

v 

Chapter 

I. 

The  Antiquity  of  Man  .     Richard  swann  lull 

1 

Chapter 

II. 

The  Natural  History  of  Man 

HARRY  BURR  FERRIS 

39 

Chapter 

III. 

The  Evolution  of  the  Nervous  System  of  Man 

GEORGE  HOWARD  PARKER 

80 

Chapter 

IV. 

The  Evolution  of  Intelligence 

JAMES   ROWLAND   ANGELL 

103 

Chapter 

V. 

Societal  Evolution    .    albert  galloway  keller 

126 

Chapter 

VI. 

The  Trend  of  Evolution   edwin  grant  conklin 

152 

Bibliography 

185 

Index 

191 

ILLUSTRATIONS 

Fig.  1.  Skulls  from  La  Chapelle-aux-Salnts,  representing 
Neandertal  man,  and  Grotte  des  Enfants,  representing 
Cro-Magnon  man Frontispiece 

Fig.     2.     Map  to  illustrate  the  broader  lines  of  dispersal  of  the 

principal  races  of  man.     After  Matthew     ....  6 

Fig.     3.     Pithecanthropus  erectus.     Skull  and  face     ....        15 

Fig.  4.  Homo  {P  ale  anthr  opus)  heidelbergensis.  Mandible 
compared  with  that  of  a  modern  European.  After 
Schoetensack 17 

Fig.     5.     Eoanthropus  dawsoni  {VAtdown  Tn2in) .    Skull  and  face       21 

Fig.     6.     Skeleton   of   Neandertal   man  compared  with   that  of 

Cro-Magnon  man 25 

Fig.     7.     Homo     {Pale  anthr  opus)     neandertalensis.      Skull    and 

face 27 

Homo  rhodesiensis.    Skull  and  face 29 

Homo  sapiens  (Cro-Magnon  man).    Skull  and  face     .        33 
Provisional  phylogeny  of  man  and  the  anthropoids       .        36 

Fertilization  of  the  ovum 41 

Four  diagrams  of  early  human  embryos  .       facing  page       42 
Human   embryo   of    1.54   mm.    (von    Spee).      X   23. 

Dorsal  view facing  page       44 

Human  embryo  of  4.2  mm.,  in  lateral  view   (His). 

X15 facing  page       44 

Developing  brain  from  a  human  embryo  of  7  mm. 

facing  page       46 
The  pallium  and  cerebellum  in  the  brains  of  various 

vertebrates facing  page       48 

The  individual  and  evolutionary  development  of  the 
nerve  cell 49 


Fig. 

8. 

Fig. 

9. 

Fig. 

10. 

Fig. 

11. 

Fig. 

12. 

Fig. 

13. 

Fig. 

14. 

Fig. 

15. 

Fig. 

16. 

Fig. 

17, 

X  ILLUSTRATIONS 

Fig.  18.  Section  through  the  spinal  cord  showing  the  early  de- 
velopment of  a  spinal  nerve  ....        facing  page       50 

Fig.   19.     Organs   developing  from   the   rudimentary   alimentary 

canal 52 

Fig.  20.     The  development  of  the  human  heart 54 

Fig.  21.     The  development  of  the  face  of  a  human  embryo  (His) 

facing  page       56 

Fig.  22.     The  relation  of  the  fetal  to  the  maternal  blood  in  the 

human  placenta facing  page       58 

Fig.  23.     Comparison   of   the   embryos   of   various  mammals  at 

corresponding  stages  of  development       .        facing  page       62 

Fig.  24.     Changes  in  proportion  during  growth 66 

Fig.  25.     Growth  curves  for  increase  in  weight  and  stature  in 

both  sexes 68 

Fig.  26.  The  caecum  and  vermiform  appendix  in  various  mam- 
mals       74 

Fig.  27.     Supernumerary  nipples  of  man 77 


CHAPTER  I 
THE  ANTIQUITY  OF  MAN 

RICHARD  SWANN  LULL 

PROFESSOR  OF   VERTEBRATE    PALEONTOLOGY,   YALE    UNIVERSITY 

The  Mosaic  account  of  the  creation,  which  has  been  and  is 
yet  of  wide  acceptance,  would  give  us  a  very  recent  date  for 
man's  advent  on  this  planet.  The  strictest  interpretation  of 
this  account  is  that  of  Doctor  John  Lightfoot,  a  profound 
Biblical  scholar,  vice-chancellor  of  Cambridge  University  in 
1654,  who  is  often  quoted  because  of  the  exactness  of  his 
findings.  As  a  result  of  careful  searching  of  the  Scripture, 
Doctor  Lightfoot  was  led  to  declare  that  "Heaven  and  earth, 
centre  and  circumference  were  made  in  the  same  instance  of 
time,  and  clouds  full  of  water,  and  man  was  created  by  the 
Trinity  on  the  26th  of  October  4004  B.  c.  at  9  o'clock  in  the 
morning." 

One  questions,  however,  not  the  Scriptural  account  but  the 
exactness  of  its  Interpretation.  The  researches  of  oriental 
scholars  are  bringing  more  and  more  Into  evidence  the  his- 
torical truth  of  the  Old  Testament  narratives,  and  are  estab- 
lishing from  other  lines  of  evidence  the  historical  character  of 
Abraham,  Isaac,  Jacob,  and  the  other  Hebrew  patriarchs,  but 
they  are  also  tracing  back  Into  a  more  and  more  remote 
period  the  history  of  the  Near  Eastern  peoples,  as  the  result 
of  the  extensive  excavations,  with  their  treasure  trove,  which 
are  being  carried  forward  in  these  venerable  abiding  places  of 
mankind. 


2  THE  EVOLUTION  OF  MAN 

Among  the  most  interesting  of  these  finds  has  been  the 
bringing  to  light  of  several  tablets,  one  of  which  is  preserved 
in  the  Yale  Babylonian  Collection,  and  which  constitute  the 
oldest  human  documents  thus  far  discovered.  These  several 
tablets  are  of  black  stone,  of  no  very  great  size,  but  bear  en- 
graven on  their  surfaces  characters  which  give  to  us  a  message 
out  of  the  past,  the  time  of  which  antedates  that  of  Christ  by 
some  5,500  to  6,000  years;  in  other  words,  a  thousand  or  more 
years  before  Doctor  Lightfoot's  date.  Nor  is  this  all,  for  the 
inscriptions  are  no  longer  in  the  so-called  picture  writing  or 
ideographs,  but  in  a  form  of  writing  undoubtedly  derived  from 
this.  They  have  progressed  so  far  along  an  evolutionary  path- 
way that  the  original  pictures  cannot  in  some  instances  be  even 
guessed  at.  This,  it  would  seem,  implies  a  centuries-long  de- 
velopmental period  before  the  beginning  of  inscriptive  writ- 
ings, and  the  inference  is  also  justifiable  that  the  protoscript 
could  not  have  been  invented  but  by  peoples  of  considerable 
intellectual  powers  who  had  long  since  emerged  from  savagery 
and  were  vastly  further  yet  removed  from  their  ultimate 
beginnings. 

The  third  line  of  evidence  is  cultural,  based  not  on  inscrip- 
tions or  documents  of  any  sort,  but  upon  the  implements  and 
weapons  of  vanished  peoples,  with  their  varying  degrees  of 
refinement.  Historic  times,  as  is  well  known,  are  often  spoken 
of  as  the  Age  of  Iron,  and  perhaps  the  Age  of  Bronze,  while 
the  prehistoric  is  called  the  Age  of  Stone.  But  the  Stone  Age 
again  has  its  subdivisions  into,  first,  the  New  Stone  Age  or 
Neolithic  period,  in  which  the  distinctive  characteristic  of  the 
implements  is  that  some  of  them  at  least  were  rubbed  smooth 
or  pohshed  after  the  preliminary  fashioning  was  completed. 
Back  of  this  period  lies  the  Paleolithic,  varying  immensely  in 
the  degree  of  perfection  of  use  and  workmanship,  so  that 
archeologists  are  agreed  upon  a  number  of  cultures  (see 
table,  infra) ,  based  upon  distinctions  some  of  which  are  evident 


THE  ANTIQUITY  OF  MAN  3 

to  the  most  casual  observer,  while  others  are  discernible 
largely  to  the  expert  only.  Back  of  the  Paleolithic  lies  the 
Eollthic,  or  Dawn  Stone  implement  period,  the  definition  of 
which  originally  implied  that  the  stone  implements  of  that 
time  were  not  artifacts  in  the  sense  of  purposeful  manufacture, 
but  that  they  were  merely  pieces  of  stone  of  convenient  size 
which  showed  the  effect  of  use.  Later  authorities  admit  of  the 
presence  of  certain  retouching  on  the  margins  of  implements 
they  still  call  eoliths,  although  just  where  they  would  draw  the 
line  between  eoliths  on  the  one  hand  and  paleoliths  of  crudest 
workmanship  on  the  other  is  not  clear.  Yet  other  authority 
would  disclaim  any  human  association  with  these  eoliths,  either 
of  use  or  manufacture,  and  invoke  the  physical  forces  of 
nature  to  account  for  their  seeming.  But  our  purpose  is  not 
to  tell  again  the  arguments,  but  merely  to  establish,  if  possible, 
on  the  basis  of  such  evidence,  a  further  criterion  for  the  test- 
ing of  man's  antiquity.  It  becomes  at  once  evident,  however, 
that  all  races  of  mankind  are  by  no  means  in  the  same  degree 
of  cultural  advancement  at  a  given  time,  and  that  for  ages  of 
human  history  the  relatively  static  and  the  highly  advanced 
peoples  must  have  dwelt  contemporaneously  in  divers  portions '^ 
of  the  earth,  just  as,  for  instance,  the  native  Tasmanians,  of 
whom  the  last  survivor  died  in  1877,  were  in  a  state  of  culture 
which  some  have  called  Eolithic  and  others  a  rather  early  stage 
of  the  Paleolithic,  perhaps  Mousterian  (Osborn).  It  becomes 
necessary  therefore  to  confine  ourselves  to  some  definite  region 
which  has  been  the  home  of  mankind  from  remote  ages,  in 
order  to  establish  a  chronological  series.  There  is  no  doubt 
in  my  mind  that  in  the  course  of  time  certain  portions  of  Asia 
will  provide  us  with  a  chronology  of  great  interest  and  amaz- 
ing antiquity,  but  thus  far  our  knowledge  of  European  cultures 
is  at  once  the  most  detailed  and  the  most  accurately  dated,  and 
the  one  with  the  fewest  omissions  in  the  series.  There  are 
readily  applied  checks  on  the  European  chronology,  for  it  has 


4  THE  EVOLUTION  OF  MAN 

been  synchronized  very  accurately  with  the  successive  advances 
and  retreats  of  the  Ice  In  the  Pleistocene  glacial  epoch,  as  well 
as  with  the  recorded  changes  In  the  faunae  of  these  several 
stages.  Hence  the  European  cultural  chronology  has  become 
the  standard  for  the  world,  and  as  It  Is  further  possible  to 
synchronize  the  periods  of  glaclatlon  In  the  Old  World  and  in 
the  New,  a  comparative  chronology  for  the  latter  may  some 
day  be  established. 

The  appended  table  is  based  upon  the  highest  authority, 
the  American  Osborn  and  the  Belgian  Rutot.  Osborn  feels 
convinced  that  Pliocene  man  is  established  by  the  Cromer 
flints  (see  page  36),  which  he  says  are  not  Eolithlc  but  Paleo- 

CHRONOLOGICAL  TABLE 


CHRONOLOGY 

INDUSTRIES 

RACES  OF  MAN 

Postglacial  time 

Magdalenian  )  Upper 
Aurignacian    )  Paleolithic 

Cro-Magnon 
Grimaldi 
?  Rhodesian 

1 

1 

1 

Of 

4th  Glacial  time 

Mousterian     )  Lower 
Acheulian       )  Paleolithic 

Neandertal 

3d  Interglacial  time 

3d   Glacial  time 

Chellean 

?  Piltdown 

2d   Interglacial  time 

2d   Glacial  time 

Heidelberg 

1st  Interglacial  time 

1st  Glacial  time 

Cromerian 

.r 

a 

Upper  Pliocene 

Foxhallian-Red  Crag 
Pre-Crag 

?  Pithecanthropus 

THE  ANTIQUITY  OF  MAN  5 

lithic  In  that  they  show  the  mark  of  fabrication;  and  to  the 
Cromer  beds  Is  assigned  a  conservative  age  estimate  of  more 
than  half  a  million  years. 

But  Europe  is  not  supposed  to  have  been  the  original  evolu- 
tionary center  of  mankind;  Its  small  size  seems  to  preclude 
that.  Rather  is  it  a  place  to  which,  as  In  historic  times,  mi- 
grating hordes  came  from  time  to  time  when  force  of  circum- 
stances drove  them  out  of  Asia  and  perhaps  more  rarely  from 
Africa.  That  Asia  is  the  birthplace  of  mankind  is  seemingly 
established,  the  following  being  some  of  the  evidences  for  this 
belief. 

Asia  possesses  great  size,  and  hence  varying  life  conditions, 
together  with  a  central  location  contiguous  to  all  other  land 
masses,  even,  as  the  north  polar  projection  shows  (Fig.  2), 
to  North  America.  From  Asia,  as  from  no  other  of  the 
continents  of  the  world,  is  communication  so  easy  and  the 
migratory  routes  so  clearly  discernible.  Asia  is  the  home  of  the 
highest  and  best  of  the  higher  organic  life  and  is  with  few 
exceptions  the  place  whence  man  has  derived  his  dependents 
and  allies,  the  domestic  animals  and  plants.  Asia  is  the  seat 
of  the  oldest  civilizations,  many  indications  of  which,  though 
visible  as  sand-drifted  ruins,  have  outlived  the  vaguest  tradi- 
tions concerning  their  origins.  Finally,  the  physical  and  cli- 
matic conditions  of  Asia  in  the  Tertiary  era  were  such  as  the 
scientist  must  postulate  In  his  Imaginings  of  the  modus  operandi 
of  human  origin  from  his  prehuman  forebears,  i.e.,  such  as 
would  enforce  descent  from  the  trees  and  terrestrial  adapta- 
tion.^ The  fact  that  the  most  primitive  peoples  to-day — 
African  pygmies  and  Australian  blackfellows — are  not  Asiatic 
does  not  tend  to  controvert  but  rather  to  strengthen  this  belief, 

1  See  Lull,  in  "Evolution  of  the  earth  and  its  inhabitants,"  Yale  University 
Press,  1918,  pp.  142-143;  and  Joseph  Barrell  "Probable  relations  of  climatic 
change  to  the  origin  of  the  Tertiary  ape-man,"  Scientific  Monthly,  January, 
1917,  pp.  16-26. 


2 


THE  ANTIQUITY  OF  MAN  7 

for  as  the  first  formed  ripples  of  the  widening  circle  caused  by 
a  stone  dropped  into  a  pool  are  the  outermost,  so  the  descend- 
ants of  the  earliest  migrants  should  to-day  be  found  farthest 
from  the  center  of  origin.  The  fact  that  the  most  ancient 
human  remains  in  point  of  time  thus  far  discovered  are  Java- 
nese and  therefore  nearer  the  focal  point  is  yet  another  bit 
of  evidence. 

It  is  with  great  confidence,  therefore,  that  one  looks  to 
Asia,  which  is  now  for  the  first  time  being  systematically  ex- 
plored by  the  American  Museum  of  Natural  History,  to  solve 
by  actual  findings  this  age-old  problem  of  human  origin. 

Fossil  Man 

Our  final  and,  to  the  paleontologist,  most  convincing  line 
of  evidence  for  man's  antiquity  lies  in  the  discovery  of  actual 
remains  of  human  beings  which  a  fortunate  combination  of 
circumstances  of  burial,  conservation,  and  subsequent  discovery 
have  brought  before  us.  That  these  are  rare  is  self-evident, 
for  even  under  the  most  favorable  conditions  for  fossilization, 
those  of  shallow-water  marine  deposits,  it  has  been  estimated 
that  but  1,044  out  of  each  100,000  different  forms  that  lived 
are  known  to  us.  Can  we  expect,  therefore,  that  the  record  of 
what  were  evidently  largely  forest-dwelling  creatures  whose 
remains  are  but  rarely  preserved  and  who  in  this  instance  un- 
doubtedly had  methods  of  disposing  of  the  dead  by  burning, 
possibly  by  consumption  as  an  article  of  diet,  or  by  merely  cast- 
ing out  to  be  devoured  by  beasts  and  birds  of  prey,  could 
possibly  be  as  perfect  as  that  of  the  marine  forms?  One 
marvels,  not  that  the  missing  links  in  our  chain  of  evidence  are 
many,  but  rather  that  we  possess  any  chain  at  all. 

Conditions  of  preservation.  There  are  but  two  conditions 
under  which  the  remains  of  man  are  ever  found:  one,  the 
older  and  rarer,  in  the  valley  sediments  of  rivers  which  deposit 
and  scour  away  and  deposit  again  in  time  of  flood  or  of  tran- 


8  THE  EVOLUTION  OF  MAN 

quil  flowing,  and  occasionally  catch  and  drown  the  unwary, 
as  they  do  to-day,  to  bury  their  remains  under  tons  of  sedi- 
ments which  are  subsequently  removed  and  their  contents 
exposed  either  by  natural  or  by  human  agencies.  The  other 
more  fruitful  source  Is  the  underground  caverns  of  Europe — 
abandoned  subterranean  river  beds  which  are  always  to  be 
found  in  limestone  countries  and  which,  when  opened  to  the 
air  through  the  eroding  away  of  overlying  materials  by  rain, 
frost,  and  snow,  formed  an  inviting  retreat  from  inclement 
weather  and  the  assaults  of  savage  beasts.  These  caverns  thus 
became  the  place  of  abode  and  often  of  sepulture  of  prehistoric 
man,  but  were  evidently  not  available  for  his  tenancy  until  com- 
paratively late  in  time  (Mousterian,  see  table,  page  4). 

Means  of  determining  antiquity.  The  criteria  for  establish- 
ing the  antiquity  of  human  remains  are  three.  First,  the 
geological  age  of  the  strata  wherein  the  remains  lie;  secondly, 
the  associated  animals  or  artifacts  or  both;  and  third,  actual 
somatological  distinctions  from  existing  man.  The  first  must 
be  most  carefully  weighed,  and  in  general  such  is  the  very 
natural  scepticism  even  among  scientists  that  it  is  well  to  have 
corroborative  evidence  by  unimpeachable  witnesses  both  of  the 
discovery  and  the  exhumation.  It  is  further  necessary  very 
carefully  to  distinguish  between  natural  deposition  of  remains 
and  intrusive  burial,  such  as  is  often  practiced  by  mankind, 
which  places  the  subject  among  objects  which  may  far  ante- 
date it  in  time.  A  scattered  skeleton  and  one  overlaid  by  abso- 
lutely undisturbed  deposits  are  both  good  criteria  of  contem- 
poraneity, but  chance  often  makes  strange  bedfellows.  Thus 
the  finding  by  the  writer  of  a  glass  bottle,  bearing  all  the 
marks  of  extremely  recent  manufacture,  beneath  the  hip  bone 
of  an  extinct  horse  in  an  apparently  undisturbed  Pleistocene 
deposit  in  Texas  was  a  little  disconcerting  until  the  looseness 
of  the  surrounding  sand  betrayed  a  filled-in  animal  burrow 
into  which  the  bottle  had  undoubtedly  been  thrust.    The  asso- 


THE  ANTIQUITY  OF  MAN  9 

ciatlon  therefore  with  extinct  animals  and  even  an  apparently 
like  degree  of  fossilization  are  not  entirely  trustworthy  when 
taken  alone.  Associated  artifacts  when  implying  ceremonial 
burial  are  fairly  safe  criteria  and  have  been  given  high  value 
in  European  age  determination. 

The  final  criterion,  that  of  anatomical  distinction,  is  of 
course  highly  valuable,  but  has  led  to  difficulties,  as,  for  in- 
stance, when  a  modern  type,  such  as  all  the  American  ones 
prove  to  be,  shows  other  indications  of  great  antiquity.  It  was 
formerly  supposed  that  there  was  but  a  single  line  of  phyletic 
descent  to  modern  man,  but  the  belief  is  gaining  ground  that, 
as  in  the  evolution  of  horses,  the  story  is  not  so  simple  as  was 
at  first  supposed,  but  that  there  were  several  lines  of  descent 
all  of  which  may  be  of  ancient  origin,  so  that  what  have  been 
called  modern  types  of  mankind  might  well  be  found  con- 
temporaneous with,  or  even  antecedent  to,  the  remains  of  more 
primitive  races.  This  will  be  discussed  in  greater  detail  below 
(page  35)- 

Record  of  Discovery 

New  World,  A  brief  resume  of  the  discoveries  of  the 
actual  osseous  remains  of  prehistoric  man  which  have  thus  far 
come  to  light  emphasizes  the  antiquity  of  his  world-wide  dis- 
tribution, but  we  are  not  yet  in  position  to  date  with  finality 
the  earlier  men  of  the  New  World.  Of  these.  North  America 
has  produced  a  number  of  specimens,  the  oldest  of  which  in 
time  of  discovery  is  the  so-called  Calaveras  skull,  found,  to- 
gether with  certain  implements,  stone  mortars  and  pestles, 
spearheads  and  hammer  stones,  embedded  in  Californian  gold- 
bearing  gravels  of  undoubted  Pliocene  age.  How  this  ma- 
terial came  there  is  a  mystery,  but  at  present  the  Calaveras 
man  is  not  supposed  to  have  been  contemporaneous  with  the 
gravels  but  to  represent  a  man  both  physically  and  culturally 
of  much  later  date. 


lo  THE  EVOLUTION  OF  MAN 

Again  and  again  such  specimens  have  come  to  light,  as  in 
the  Trenton  gravels  which  date  from  the  final  retreat  of  the 
ice,  the  Nebraska  loess  man  near  Omaha,  the  Lansing  man, 
and  that  of  Vero,  Florida,  where  the  remains  of  like  degree 
of  fossilization  with  their  animal  associates  were  found  en- 
tombed with  creatures  of  undoubted  Pleistocene  affinities.  Still 
other  finds  are  those  at  Rancho  La  Brea  in  the  Pleistocene 
asphalt  of  California,  and  lastly  at  Dallas,  Texas,  in  the 
Lagow  sand  pit,  associated  with  a  Pleistocene  fauna  recently 
described  by  the  writer.  Not  one  of  these,  despite  their  ful- 
filment of  every  other  prerequisite  to  antiquity — burial  in  older 
strata,  animal  association,  like  degree  of  fossilization,  and 
so  forth — meets  the  requirements  of  the  physical  anthropolo- 
gist, for  none  shows  somatological  characters  which  are  not 
possessed  by  the  modern  American  Indians.  This  leads 
Doctor  Hrdlicka  to  doubt  their  antiquity,  but  a  growing  con- 
viction in  the  author's  mind,  stimulated  by  so  high  an  authority 
as  Sir  Arthur  Keith,  of  the  Royal  College  of  Surgeons,  Lon- 
don, is  that,  on  the  other  hand,  they  may  in  part  be  of  genuine 
Pleistocene  age  and  hence  point  to  the  high  antiquity  of  the 
Indian  type. 

The  South  American  record  is  comparable.  Florentino 
Ameghino  (19 12)  described  supposedly  human  forms  under 
the  names  of  Tetraprothomo  and  Diprothomo,  based  upon 
remains  which  in  at  least  one  instance  owed  their  peculiarity  to 
the  fact  that  they  were  not  even  human.  But  in  no  event  were 
these  so-called  men  as  old  or  as  primitive  structurally  as 
Ameghino  would  have  us  believe,  and  his  thesis  that  South 
America  may  have  been  the  radiation  center  of  the  human 
stock  seems  untenable. 

If  none  of  the  New  World  men  are  of  archaic  cast,  their 
association  with  extinct  forms,  as  for  instance  with  the  masto- 
don in  the  north  and  with  living  ground  sloths  in  the  south, 
seems  to  bear  the  mark  of  authenticity.     The  most  authentic 


THE  ANTIQUITY  OF  MAN  ii 

northern  Instance  is  that  described  by  Doctor  J.  M.  Clarke,  of 
the  association  In  Attica,  New  York,   of  mastodon  remains 

ith  charcoal  and  pottery.  Four  feet  below  the  surface,  in  a 
black  muck,  Clarke  found  the  bones  of  the  mastodon,  and 
twelve  Inches  below  this.  In  undisturbed  clay,  pieces  of  pottery 
and  thirty  pieces  of  charcoal.  The  association  of  the  mastodon 
with  the  charcoal  is  not  so  significant,  as  It  Is  conceivable  that 
charcoal  may  have  been  formed  by  natural  means,  but  not 
the  pottery.  The  Issue  of  the  magazine  Natural  History  for 
November-December,  192 1,  figures  what  seems  to  be  the  crude 
outline  of  a  mastodon  on  a  piece  of  bone  from  Jacob's  cavern, 
Plnevllle,  Missouri,  in  a  way  comparable  to  the  Upper  Paleo- 
lithic engravings  of  Europe. 

In  South  America,  again,  the  association  of  man  and  the 
ground  sloth,  Grypotherium,  in  a  cavern  at  Lost  Hope  Inlet, 
Patagonia,  seems  definitely  established.  The  fresh-looking 
remains,  shreds  of  skin  which  show  indications  of  having  been 
cut  with  primitive  knives,  the  presence  of  apparently  cut  grass, 
all  point  to  the  cherishing  by  man  of  what  were  probably  the 
last  of  these  creatures,  either  In  the  role  of  domestic  animals 
or  of  those  sacred  to  some  deity  as  was  the  Egyptian  bull 
Apis. 

Keith  is  greatly  impressed  with  the  diversity  of  American 
languages  and  the  high  development  of  pre-Columbian  civiliza- 
tions in  the  New  World,  and  feels  that  they  point  to  an  an- 
tiquity far  beyond  that  commonly  accepted  by  the  ethnologist. 
On  the  other  hand,  all  indigenous  New  World  men  are  of 
essentially  the  same  general  racial  type,  the  Mongoloid,  nor 
have  they  been  here  long  enough  to  establish  racial  differentia- 
tion comparable  to  that  of  the  Old  World. 

Old  World.  Africa  has  been  productive  of  but  two  osseous 
specimens  of  man  of  marked  antiquity.  One,  found  at  Oldo- 
way  ravine,  Tanganyika  Territory,  in  the  early  days  of  the 
Great  War,  Is  impressive  neither  for  its  apparent  age  nor 


12  THE  EVOLUTION  OF  MAN 

its  somatologlcal  peculiarities.  The  latest  find,  however,  from 
Broken  Hill  mine  in  northern  Rhodesia,  has  aroused  a  great 
deal  of  interest,  because,  while  not  very  decisively  dated  and 
associated  with  a  recent  fauna  all  of  which  are  either  now 
alive  or  were  so  at  the  coming  of  white  men,  the  skull  itself  is 
of  a  most  peculiar  and  interesting  type,  clearly  not  that  of 
modern  man.  And  the  finding  of  a  second  specimen  which, 
while  fragmentary,  serves  nevertheless  to  show  community  of 
type  with  the  first,  seems  to  establish  the  remains  as  repre- 
sentatives of  a  race  and  not  due  to  individual  peculiarities. 

Arguments  such  as  those  recently  offered  by  Churchward^ 
striving  to  prove  the  ancestral  character  of  the  African  Bush- 
men and  the  fact  that  Africa  may  be  the  primal  home  of  man- 
kind are  not  yet  established  theses.  Northern  Africa  in  the 
Barbary  States  has  produced  cavern  murals  comparable  to 
those  in  southern  Europe,  and  Sollas  has  made  much  of  Bush- 
man affinities  in  all  of  these  artistic  remains,  but  these  are  late 
in  time  (Upper  Paleolithic,  Magdalenian)  and  do  not  aid  us 
in  our  establishment  of  high  antiquity  for  African  man.  Un- 
doubtedly Africa  is  an  old,  old  home  of  mankind — all  signs 
point  to  that  conclusion — but  the  actual  skeletal  remains  of 
types  anterior  to  our  own  species  are,  as  we  have  shown,  but 
a  single  find.  This  is  undoubtedly  due  largely  to  paucity  of 
discovery  rather  than  to  lack  of  occurrence. 

Of  Asia,  a  similar  tale  is  told.  Pithecanthropus,  found  in 
1 89 1  in  Trinil,  Java,  being  still  unique,  although  one  looks 
daily  for  the  announcement  of  further  finds  as  the  outcome  of 
the  American  Museum's  Asiatic  expedition  now  in  the  field. 
Again,  we  simply  do  not  know  the  country  paleontologically. 

At  Darling  Downs,  Australia,  a  human  skull  has  been  found, 
apparently  in  association  with  extinct  Pleistocene  Mammalia. 

The  European  finds,  on  the  other  hand,  are  relatively  so 

2  A.  Churchward,  "The  origin  and  evolution  of  the  human  race,"  New  York 
and  London  (Macmillan),  1922. 


THE  ANTIQUITY  OF  MAN  13 

numerous  that  as  we  have  established  our  cultural  chronology 
upon  European  discovery,  so  we  must  base  our  conception  of 
human  antiquity  and  evolutionary  lines  largely  upon  European 
material.  For  Europe  is  small,  accessible,  and  the  home  of  an 
enthusiastic  band  of  workers  whose  efforts  have  been  untiring 
and  whose  results  are  already  at  hand,  although  much  will 
come  to  light  in  the  future. 

I  Prehistoric  Human  Species 

Pithecanthropus  erectus 
Taken  in  order  of  chronological  sequence,  the  Asiatic  Pithe- 
canthropus stands  first,  as  it  does  in  most  respects  in  the  char- 
acteristics which  it  betrays.  Found  in  1891  in  the  deposits  of 
the  Bengawan  River,  near  Trinil,  on  the  island  of  Java,  these 
fragments  of  humanity  are  most  meager,  but  such  as  they  are, 
they  throw  a  flood  of  light  on  human  origins.  It  is  to  be  re- 
gretted, however,  that  their  owner.  Doctor  Dubois,  a  Dutch 
army  surgeon,  now  professor  of  physical  geography  in  the 
University  of  Amsterdam,  will  not  permit  their  further  study 
by  his  colleagues.  Our  knowledge  therefore  is  based  on  Du- 
bois's own  admirable  researches,  together  with  the  wide- 
spread replicas  of  the  external  aspect  of  the  calvarium,  which 
have  enabled  some  independent  conclusions  to  be  drawn.  The 
remains  include  the  skull-cap,  three  teeth  (M^  left,  M^  right, 
P2  left) ,  and  a  left  femur,  the  last  bearing  an  exostosis  indica- 
tive of  injury  or  disease.  These  probably  pertain  to  a  single 
individual,  although  they  were  found  scattered  through  some 
twenty  yards  of  space  and  were  not  all  discovered  at  the  same 
time.  This  scattering  precludes  the  possibility  of  intrusive 
burial,  however.  The  most  careful  search  has  failed  to  reveal 
any  further  fragments,  although  a  special  expedition  under 
Madame  Selenka,  which  brought  to  light  the  third  tooth, 
carried  on  extensive  excavations.     So  much  has  been  written 


14  THE  EVOLUTION  OF  MAN 

concerning  this  type  of  man  that  the  summary  of  conclusions, 
which,  however,  lack  the  finality  of  finished  research,  is  all 
that  need  be  given  here. 

The  skull-cap  is  dolichocephalic,  estimates  of  the  cranial 
capacity  varying  from  710  to  1,060  c.c.  as  compared  with  930 
to  2,000  c.c.  for  modern  man.  The  brain,  while  human  in  some 
respects,  is  subhuman  in  others,  especially  in  that  area  in  which 
the  memories  of  past  impressions  derived  from  the  higher 
senses  are  recorded.  Whether  or  not  speech  was  actually  used 
is  questioned,  but  the  possibility  of  it  seems  clear. 

The  straightness  of  the  thigh  as  compared  with  that  of 
Neandertal  man  (see  infra,  page  24)  is  marked,  so  that  in 
Pithecanthropus  the  posture  must  have  been  as  fully  erect  as  in 
modern  man.  In  this  he  is  in  no  sense  a  transitional  form  but 
in  skull  characters  he  is,  for  the  shape  of  the  thigh  is  corre- 
lated with  that  of  other  parts,  the  vertebral  column  with  its 
curves,  the  pelvis,  and  the  poise  of  the  skull,  all  of  which,  one 
may  infer,  were  distinctly  human. 

The  teeth  of  the  Java  man  are  also  of  a  distinctly  human 
type,  showing  no  shortening  of  the  roots  or  development  of 
the  pulp  cavity,  to  which  Keith  has  applied  the  term  "tauro- 
dont"  (ox-tooth),  as  in  the  Heidelberg  and  Neandertal  races 
to  be  described  later.  The  alternative  type  of  teeth  he  calls 
"cynodont"  (dog-tooth),  such  as  those  of  modern  man  and 
the  apes,  adapted  to  a  more  varied  and  less  harsh  diet.  Pithe- 
canthropus had  teeth  of  the  latter  type.  The  tooth  crowns  are 
wider  than  long,  the  reverse  of  simian  dimensions,  and  al- 
though they  do  show  certain  minor  ape-like  characters,  they 
also  show  certain  degenerative  features. 

Gregory  (1920,  page  690)  thus  sums  up  the  status  of  Pithe- 
canthropus: 

The  association  of  gibbon-like  skull-top,  modernized  hu- 
man femur  and  subhuman  upper  molars  with  reduced  pos- 
terior moiety,  if  correctly  assigned  to  one  animal,  may  perhaps 


THE  ANTIQUITY  OF  MAN  15 

define  Pithecanthropus  as  an  early  side  branch  of  the  Homini- 
dae,  which  had  already  been  driven  southward  away  from 
the  primitive  center  of  dispersal  in  Central  Asia,  by  pressure 
of  higher  races.  But  whatever  its  more  precise  systematic 
and  phylogenetic  position,  Pithecanthropus,  or  even  its  con- 
stituent parts,  the  skull-top,  the  femur  and  the  molars,  sever- 
ally and  collectively  testify  to  the  close  relationship  of  the  late 
Tertiary  anthropoids  with  the  Pleistocene  Hominidae. 


^ 


Fig.  3.    Pithecanthropus  erectus.     Skull  and  face.    Adapted  from  McGregor. 
Portion  beneath  irregular  line  restored.     Two  fifths  natural  size. 

Of  restorations  of  Pithecanthropus ,  several  have  been  at- 
tempted. The  skull  completion  here  shown  (Fig.  3)  is  derived 
from  the  studies  of  Dubois  and  McGregor.     The  latter  has 


1 6  THE  EVOLUTION  OF  MAN 

done  an  admirable  bust  based  on  the  most  careful  detailed 

study.^ 

Pithecanthropus  was  found  associated  with  twenty-four  or 
more  species  of  mammals,  all  of  which  are  now  extinct  and 
whose  affiliations  are  distinctly  Pliocene.  Gregory  (1921, 
page  691,  Fig.  270)  shows  this  ancient  relic  as  of  upper  Siwalik 
age  (Pliocene).  Dubois  considered  its  assignment  to  late 
Pliocene  and  therefore  equivalent  to  the  Cromer  forest  beds 
of  England  (see  infra).  Keith  describes  its  geologic  occur- 
rence as  follows:  under  the  fossiliferous  bed  is  a  stratum  of 
conglomerate,  then  a  layer  of  clay  laid  down  in  quiet  muddy 
water,  under  the  clay  a  marine  deposit  containing  early  Plio- 
cene fossil  shells  corresponding  to  the  "Crag"  of  East  Anglia. 
Over  the  fossil  beds  containing  Pithecanthropus  are  stratified 
deposits  forty-five  feet  in  thickness,  recalling  the  Mauer  sands 
(see  page  17).  In  terms  of  years,  a  conservative  estimate 
would  give  to  Pithecanthropus  an  age  of  400,000  to  500,000, 
or  in  round  numbers  approximately  half  a  million  years. 

Heidelberg  Man  {Homo  {P ale anthr opus)  heidelbergensis) 

The  jaw  upon  which  this  species  is  based  bears  the  unique 
distinction  of  having  caused  no  controversy  whatever  among 
anthropologists,  for  the  absolute  perfection  of  the  specimen, 
the  stratigraphic  position,  and  the  circumstances  of  its  dis- 
covery leave  no  ground  at  all  for  doubt  or  dispute.  It  came 
to  its  fortunate  discoverer.  Doctor  Otto  Schoetensack,  as  the 
just  reward  of  some  twenty  years  of  patient  scrutiny  and 
expectation.  It  was  found  at  Mauer  in  southern  Germany  in 
1907.  This  little  village  lies  in  the  valley  of  the  Elsenz,  a  trib- 
utary of  the  more  famous  Neckar,  and  at  a  distance  of  ten 

3  See  Lull  "Organic  evolution,"  Macmillan,  1917,  PI.  XXX,  Fig.  A.  Mc- 
Gregor's restorations,  and  those  of  Rutot,  are  reproduced  in  Osborn's  "Men  of 
the  Old  Stone  Age."  Rutot's  are  also  to  be  found  in  "Prehistoric  man  and  his 
story,"  by  G.  F.  Scott  Elliot,  Seeley,  Service  &  Co.,  1915. 


THE  ANTIQUITY  OF  MAN  17 

kilometers  southeast  from  the  city  of  Heidelberg,  famed  for 
being  one  of  the  oldest  seats  of  scientific  learning  in  central 
Europe.  The  Mauer  sands  are  river  valley  deposits,  the  upper 
portion  of  which  is  regarded  by  Schoetensack  as  upper,  the 
rest  as  lower.  Pleistocene.  From  this  locality  has  come  a 
fauna  of  mammals  which  compares  with  that  of  the  pre-Glacial 
forest  beds  of  Norfolk,  England.  The  jaw  itself  was  found 
in  the  lower  portion,  about  seventy-nine  feet  below  the  summit 
of  the  deposits. 


Fig.  4.  Homo  {Paleanthropus)  heidelbergensis.  Mandible  compared  with 
that  of  a  modern  European  (broken  line).  After  Schoetensack.  Two  thirds 
natural  size. 


The  lower  jaw  is  complete  to  the  last  detail,  although  the 
teeth  of  the  left  side,  which  adhered  to  a  limestone  pebble, 
were  broken  off  upon  the  removal  of  the  latter.  They  are, 
however,  carefully  preserved,  and  the  accident  brought  to  light 
yet  other  characteristics  not  otherwise  visible. 

The  jaw  is  very  primitive,  heavy,  and  massive.  It  lacks 
entirely  the  chin  prominence  so  characteristic  of  modern  man, 
as  the  front  profile  of  the  jaw  slopes  away  as  does  that  of  a 


1 8  THE  EVOLUTION  OF  MAN 

gorilla.  Within  the  jaw  at  the  symphysis  there  is  the  genial 
pit  for  the  attachment  of  the  tongue  muscles  as  in  the  anthro- 
poids, and,  like  them,  the  bone  encroaches  on  the  floor  of  the 
mouth.  In  both  these  respects  the  jaw  is  more  simian  than 
human  but  not  sufficiently  so  to  preclude  the  possibility  of  rudi- 
mentary speech.  The  body  of  the  jaw  is  not  unlike  that  of 
the  successor  of  Heidelberg  man,  the  Neandertal  race,  but  the 
ascending  branch  which  gave  attachment  for  the  masticating 
muscles  differs  in  shape,  being  gibbon-like,  and  is  much  greater, 
as  great  in  fact  as  that  of  a  female  orang.  The  teeth,  while 
actually  large,  are  relatively  small,  and  the  taurodontism  is 
developed  in  a  marked  degree,  as  shown  by  the  enlarged  pulp 
cavity,  dilated  crowns,  and  abbreviated  roots.  The  teeth  are 
regularly  placed  and  the  canines  are  not  in  any  way  bestial  in 
their  development,  less  so,  indeed,  than  in  some  modern  men. 
Without  the  teeth,  the  Heidelberg  jaw  might  well  be  con- 
sidered as  that  of  an  ape,  but  the  teeth  affirm  its  human  affini- 
ties although  in  their  development  and  in  the  form  of  the 
dental  arch  they  are  prophetic  of  Neandertal,  not  of  modern, 
man.  Keith  does  not  believe  that  either  Heidelberg  or  Nean- 
derthal man  lies  in  the  direct  line  of  modern  descent,  but  that 
the  taurodont  dentition  implies  a  specialization  for  a  rough 
herbivorous  diet  and  that  in  this  respect  both  races  show  a 
departure  from  the  more  simian  dentition  and  implied  feeding 
habits  of  the  main  line  of  descent  into  Homo  sapiens. 

While  the  skull  of  Heidelberg  man  is  yet  unknown.  Doctor 
McGregor  has  nevertheless  attempted  its  reconstruction,  for 
of  course  many  dimensions,  as  well  as  the  character  of  the 
upper  teeth,  can  be  learned  from  the  lower  jaw,  while  the  re- 
mainder of  the  skull  was  studied  from  Its  Neandertal  succes- 
sor. The  result  Is  a  pre-Neandertal  skull,  elongated,  with  a 
low  forehead,  prominent  brow-ridges,  and  a  rounded  dental 
arch,  and  there  Is  reason  to  believe  that  this  reconstruction  will 
prove  prophetic  when  the  actual  cranium  is  revealed  to  us  by 


THE  ANTIQUITY  OF  MAN  19 

discovery,  unless  the  latter  shows  certain  unique  and  entirely 
unexpected  features. 

The  probable  contemporaneity  of  the  associated  fauna  with 
that  of  the  pre-Glacial  forest  beds  has  already  been  men- 
tioned. Osborn  in  19 15  considered  both  the  fauna  and  the 
jaw  to  pertain  to  the  Second  Interglacial  time,  but  Schoeten- 
sack,  Geikie,  and  others  would  assign  them  to  the  First  Inter- 
glacial (Lower  Pleistocene).  Gregory  says  (1921,  page 
126): 

If  of  Lower  Pleistocene  age,  the  Heidelberg  jaw  shows 
that  the  most  important  diagnostic  characters  of  the  dentition 
of  the  Hominidae  had  already  been  acquired  at  the  beginning 
of  the  Pleistocene  epoch  and  indicates  that  prehuman  transi- 
tional conditions  must  be  sought  in  earlier  geological  ages. 
If,  on  the  other  hand,  the  Heidelberg  jaw  dates  only  from  the 
Middle  Pleistocene,  then  transitional  conditions  may  be  looked 
for  as  late  as  the  Lower  Pleistocene  or  Upper  Pliocene. 

The  age  of  this  venerable  relic  read  in  terms  of  years  is  at 
least  400,000,  and  the  associated  flints  are  Eolithic  in  culture. 

The  Dawn  Man  of  Piltdown  {Eoanthropus  dawsoni) 

This  is  by  far  the  most  ancient  English  human  relic  thus  far 
discovered,  although  there  is  some  question  as  to  the  precise 
dating  and,  owing  to  the  fragmentary  character  of  the  ma- 
terial when  it  came  into  scientific  hands,  it  has  aroused  a  great 
deal  of  controversy,  in  marked  contrast  with  the  unhesitating 
acceptance  of  the  jaw  of  Heidelberg.  The  specimen  was 
found  at  Piltdown,  on  the  Ouse,  Sussex,  in  a  shallow  stratum 
of  gravel,  less  than  four  feet  in  thickness  at  the  point  of  dis- 
covery. This  gravel  rests  on  a  bed-rock  of  Mesozoic  age,  the 
Hastings  beds.  From  the  lowest  six-inch  layer  of  the  Pilt- 
down gravels,  where  everything  is  stained  a  deep  brown,  came 
the  skull,  together  with  certain  crude  (Eolithic)  implements 
and  the  remains  of  several  animals,  long  since  extinct.     This 


20  THE  EVOLUTION  OF  MAN 

pit  has  been  worked  for  some  time  for  road-mending  flints 
and  thither  occasionally  came  Mr.  Charles  Dawson,  a  local 
lawyer  and  antiquarian,  to  secure  the  flint  implements  which 
from  time  to  time  came  to  light.  One  day  a  workman  gave 
Mr.  Dawson  a  fragment  of  the  skull  parietal.  This  started  a 
long  search,  ultimately  resulting  in  the  finding  of  other  char- 
acteristic portions  of  the  cranium,  a  ramus  of  the  jaw  with 
several  molars  in  situ,  a  canine  tooth,  and  two  nasal  bones. 
These  fragments,  which  represented  what  was  at  first  an  entire 
skull  unwittingly  shattered  by  a  workman's  pick,  were  sub- 
mitted to  Doctor  Arthur  Smith  Woodward  of  the  British 
Museum,  who  began  the  laborious  process  of  reconstruction 
of  a  complete  skull  from  the  several  isolated  pieces.  It  is  but 
natural  that  among  the  several  workers  who  essayed  the  same 
task,  Smith  Woodward,  Keith,  and  McGregor,  there  should 
be  some  difference  of  opinion,  which  is  manifest  principally  in 
a  little  variation  as  to  the  estimate  of  skull  capacity.  But  in 
the  main  there  is  agreement  as  to  the  general  form.  The 
cranium  is  extremely  thick-walled,  averaging  four  tenths  of 
an  inch,  with  a  rather  steep,  though  contracted  and  ape-like 
forehead,  and  one  that  lacks  the  prominent  brow-ridges  of 
Neandertal  man.  The  skull  was  nicely  balanced  on  the  neck  as 
in  ourselves,  implying  an  erect  posture  in  further  contrast  to 
the  men  of  Neandertal.  The  brain-cast  was  submitted  to  the 
high  authority  of  Professor  Elliot  Smith,  who  pronounced  it 
the  "most  primitive  and  most  simian  human  brain  thus  far 
recorded." 

The  jaw  has  proved  to  be  a  veritable  bone  of  contention. 
Everything  pointed  to  community  of  origin  with  the  cranium, 
except  its  remarkably  primitive  character.  One  American 
authority,  G.  S.  Miller,  Jr.,  who  studied,  not  the  original  but 
a  cast,  came  to  the  conclusion  that  the  jaw  and  skull  could  not 
possibly  pertain  to  the  same  individual  or  even  the  same  genus, 
but  that  the  former  was  that  of  a  fossil  chimpanzee,  to  which 


THE  ANTIQUITY  OF  MAN 


21 


Fig.  5.    Eoanthropus  daivsoni   (Piltdown  man).     Skull  and  face.    Adapted 
from  McGregor.    Two  fifths  natural  size. 


the  technical  name  of  Pan  vetus  was  given,  despite  the  fact  that 
fossil  anthropoids  were  heretofore  unknown  in  England.  In 
this  conclusion  Mr.  Miller  has  had  quite  a  large  American  fol- 
lowing. The  matter  has,  however,  been  settled  beyond  ques- 
tion by  the  finding  of  a  second  specimen  of  the  Piltdown  man 
some  two  miles  distant,  consisting  of  diagnostic  cranial  frag- 
ments associated  again  with  a  lower  molar  of  precisely  similar 
character  to  those  in  the  first  jaw,  a  happening  which  could 


22  THE  EVOLUTION  OF  MAN 

hardly  occur,  according  to  the  law  of  probabilities,  in  both  of 
the  only  known  instances  if  the  jaw  and  skull  were  not  those 
of  the  same  form. 

The  jaw  is  indeed  peculiar,  as  the  symphysis  is  distinctly 
simian,  while  according  to  Keith,  the  rear  part  is  as  distinctly 
human.  The  whole,  taken  together  with  the  canine  tooth, 
points  to  a  man  of  bestial  visage,  united  with  a  rather  modern- 
looking  cranium,  a  combination  which  excludes  him  from  our 
species  and  genus,  and  to  which  the  name  Eoanthropus  daW' 
soni  is  most  aptly  applied,  no  one,  as  Keith  says,  having  ever 
anticipated  the  discovery  of  one  of  man's  progenitors  showing 
such  a  remarkable  mixture  of  human  and  simian  characters. 
Chief  among  the  peculiarities  of  the  jaw  is,  therefore,  the 
symphysis,  which  is  even  more  simian  than  that  of  Heidelberg 
in  that  there  is  no  rudiment  or  suggestion  of  the  forming  chin. 
The  ape-like  genial  pit  is  present,  together  with  the  encroach- 
ment of  bone  on  the  floor  of  the  mouth.  The  anterior  teeth, 
so  far  as  known,  are  also  simian,  while  the  molars  are  human, 
although,  as  Gregory  says,  extremely  like  those  of  a  chimpan- 
zee, but  these,  in  turn,  are  closely  related  in  pattern  to  primi- 
tive human  molars. 

As  has  been  said,  very  primitive  eoliths,  stained  brown,  were 
found  actually  associated  with  the  skull;  in  the  gravel  above, 
however,  the  flints  are  a  brilliant  colored  iron  red  and  of  such 
degree  of  workmanship  that  Dawson  considers  them  as  Chel- 
lean  or  at  the  earliest  pre-Chellean  in  age.  The  man,  however, 
as  has  been  said,  was  not  buried  down  into  the  older  strata 
but  contemporaneous  therewith,  possibly  the  result  of  a  drown- 
ing accident.  The  British  authorities,  Lewis  Abbott  and 
J.  Reid  Moir,  both  refer  the  older  gravels  to  the  Pliocene,  but 
the  more  widely  accepted  belief  is  that  the  Piltdown  man  is 
Lower  Pleistocene,  of  Second  or  Third  Interglacial  time,  so 
that  in  terms  of  years  his  age  is  from  200,000  to  300,000 
years. 


THE  ANTIQUITY  OF  MAN  23 

These  remains  occurred  so  near  the  present  land  surface 
that  had  they  not  shown  evidence  of  great  structural  antiquity, 
their  authenticity  would  be  greatly  in  doubt.  As  it  is,  they  are 
conceded  to  be  ancient,  the  chief  discussion  being  as  to  how 
ancient  and  whether  or  not  the  jaw  pertained,  whether  the 
canine  tooth  was  upper  or  lower,  and  finally  as  to  the  cubic 
contents  of  the  skull.     (See  Fig.  5.) 

Neandertal  or  Mousterian  man  {Homo  neandertalensis  or 

primigenius) 

This  is  now  a  well-established  race  with  considerable  range 
of  variation  within  it,  for  of  it  there  have  been  found  rela- 
tively numerous  individuals  of  greater  or  less  degree  of  per- 
fection. Of  these,  the  first  in  chronological  order,  and  the 
most  ancient  in  point  of  time,  is  the  Gibraltar  skull  discovered 
in  1848,  but  unappreciated  scientifically  for  so  many  years  that 
its  position  in  the  series  has  been  subordinate  instead  of  at  the 
head.  It  is  now  preserved  in  the  Museum  of  the  Royal  Col- 
lege of  Surgeons. 

The  most  famous  skeleton,  which  gave  its  name  to  the 
race,  is  that  found  at  the  mouth  of  a  cave  in  the  Neandertal 
gorge  of  the  valley  of  the  Dussel,  a  German  tributary  of  the 
Rhine.  While  apparently  nearly  perfect  at  the  time  of  dis- 
covery, but  little  of  the  skeleton  is  now  preserved  in  the  Pro- 
vincial Museum  at  Bonn.  A  skull-cap,  ribs,  part  of  a  right 
scapula,  clavicle,  humeri,  ulnae,  femora,  right  radius,  tibia,  and 
a  portion  of  the  left  pelvic  bone  are  the  chief  parts  remaining, 
and,  as  might  well  be  supposed,  the  publication  of  the  find 
gave  rise  to  much  contention  as  to  whether  it  represented  a 
type  of  man  or  was  merely  the  relic  of  some  poor  waif  of 
humanity,  diseased  or  otherwise,  the  result  of  abnormal 
growth.  It  was  not  until  the  further  discovery  of  two  other 
individuals  at  Spy  in  Belgium  in  1886,  which  again  bore  the 


24  THE  EVOLUTION  OF  MAN 

distinguishing  features  of  Neandertal  man,  that  it  was  fully 
conceded  that  they  represented  a  race,  and  that  the  character- 
istics which  they  exhibited  were  diagnostic.  Later  finds, 
though  not  in  chronological  order,  have  been  made  at  the 
following  places : 

Le  Moustier,  La  Chapelle-aux-Saints,  La  Ferrassie,  La 
Quina,  and  Pech  de  I'Aze,  France;  Banolas,  Spain;  La  Nau- 
lette  in  the  Lesse  Valley,  Belgium;  Ehringsdorf  near  Weimar, 
Germany;  Krapina,  Austria. 

The  anatomical  features  of  the  Neandertal  race  are  now 
very  well  known,  largely  through  the  very  detailed  studies  of 
Professor  Marcelin  Boule  on  the  material  from  La  Chapelle- 
aux-Saints  in  the  Paris  Museum.  Homo  neandertalensis  was 
of  low  stature,  hardly  exceeding  five  feet  three  inches  for  the 
males  and  less  for  the  females.  The  posture  was  not  fully 
erect,  as  shown  by  the  curved  thigh  bones,  the  absence  of  the 
cervical  flexure  of  the  spine,  and  the  position  of  the  foramen 
magnum  of  the  skull.  The  head  was  borne  on  the  immensely 
muscular  neck  in  such  a  way  that  the  face  was  thrust  forward 
in  an  ape-like  manner,  thus  lacking  the  delicate  poise  which  it 
would  possess  were  the  carriage  fully  erect. 

The  skeleton  of  Neandertal  man  is  peculiar,  not  alone  in 
the  lack  of  the  fourth  flexure  of  the  vertebral  column  and  in 
the  presence  of  curvature  in  the  thigh,  but  in  the  enlarged 
articulation  of  the  limbs,  with  knee  and  hip  joints  somewhat 
bent,  and  in  the  peculiarly  rounded  ribs,  all  of  which  point  to 
a  clumsy,  shuffling,  loose-jointed  being  of  great  muscular 
power.  The  distal  segments  of  the  limbs  are  relatively  short, 
in  marked  contrast  with  those  of  the  great  man  of  Cro- 
Magnon  described  below,  and  the  thumbs  could  not  be  so 
freely  opposed  to  the  other  digits,  with  a  resultant  lack  of  hand 
skill. 

The  skull  of  Neandertal  man  is  very  large,  with  a  cranial 
capacity  of  i,6oo  c.c.   (La  Chapelle)   as  against  an  average 


THE  ANTIQUITY  OF  MAN 


25 


o> 


Fig.  6.     Skeleton  of  Neandertal  man  (left)  compared  with  that 
of  Cro-Magnon  man.    From  Lull,  after  Boule  and  Verneau. 


26  THE  EVOLUTION  OF  MAN 

modern  cubic  content  of  about  1,400  c.c.  The  skull  is  long,  as 
are  all  prehistoric  crania,  but  the  vault  is  low  and  the  hinder 
part  curiously  depressed  and  broadened  out,  "bun-shaped," 
as  Keith  expresses  it,  which,  together  with  the  great  apparent 
musculature  of  the  neck,  must  have  increased  the  peculiarity  of 
his  appearance.  Anteriorly,  the  supra-orbital  ridges  or  tori 
are  greatly  developed  and  are  confluent  across  the  forehead, 
not  divided  into  two  parts  by  a  median  depression  as  with 
modern  man.  The  nasal  bridge  is  depressed  and  the  upper 
jaw  very  deep,  indicating  a  long  upper  lip.  The  lower  jaw  is 
not  unlike  that  of  Heidelberg,  nevertheless  it  shows  a  distinct 
advance  over  the  latter  in  that,  while  the  chin  prominence  is 
yet  lacking,  there  is  indication  that  dental  reduction,  already 
in  evidence,  is  beginning  to  cause  a  recession  of  the  tooth-line 
to  a  position  more  nearly  above  the  chin,  giving  the  latter  a 
greater  relief.  The  lower  border  of  the  mandible  is  not  so 
much  broadened  out  to  give  play  to  the  tongue  muscles  as  in 
modern  man,  hence  potential  speech  is  less  developed.  (See 
Fig.  I  (Frontispiece)  and  Fig.  7.) 

The  teeth  are  of  the  taurodont  character  defined  above, 
large  of  pulp  capacity  and  short  of  root,  again  an  adaptation, 
according  to  Keith,  to  a  coarse  vegetative  diet.  In  teeth  and 
palate  form,  Neandertal  man  shows  a  greater  degree  of  spe- 
cialization than  does  our  own  race  and  this  in  a  form  in  other 
respects  more  primitive. 

The  brain  of  this  man  was  not  as  yet  sufficiently  advanced 
to  learn  to  substitute  other  and  more  effective  devices  for 
various  needs,  so  that  the  jaws  still  had  varied  uses  in  contrast 
with  their  very  restricted  function  to-day. 

The  brain  itself  shows  a  certain  specialization  in  its  size, 
but  the  relative  development  of  those  parts  wherein  lay  the 
higher  mental  functions  was  not  great.  Nevertheless,  Nean- 
dertal man  was  a  skilled  worker  in  flints,  had  harnessed  fire, 
and  by  the  reverential  burial  of  his  dead  surrounded  by  beau- 


THE  ANTIQUITY  OF  MAN 


27 


r 


Fig.  7.     Homo   {Paleanthropus)  neandertalensis.     Skull  and  face.     Adapted 
from  McGregor  and  Boule.    Two  fifths  natural  size. 


tifully  wrought  objects  whose  surrender  implied  a  very  real 
sacrifice  on  the  part  of  the  survivors,  together  with  apparent 
food,  had  in  greatest  probability  a  belief  of  some  sort  in 
immortality. 

It  is  in  the  form  of  the  cranial  cavity  and  of  the  supra- 
orbital ridges  that  the  Neandertal  skull  departs  most  widely 
from  that  of  modern  man,  and  it  is  in  these  two  points  that  the 


28  THE  EVOLUTION  OF  MAN 

resemblance  with  the  anthropoids  Is  most  pronounced.  They 
are  both,  however,  in  part  at  least,  explicable  as  a  response  to 
great  muscular  development  of  neck  and  jaw.  As  Keith  says 
of  him,  certain  peculiarities  of  his  were  distinctly  simian,  but 
not  all  of  them,  as  he  possessed  other  traits  distinctly  his  own. 

The  following  ideas  have  been  advanced  concerning  the 
status  of  this  interesting  race:  that  he  was  the  product  of 
disease;  that  he  was  ancestral  to  modern  man,  representing 
the  Pleistocene  stage  in  human  evolution;  that  he  was  merely 
an  extreme  variant  of  modern  man  himself,  who  had  retained 
an  unusual  share  of  ape-like  traits.  The  present  opinion,  how- 
ever, looks  upon  him  as  '*a  separate  and  peculiar  species  of 
man  which  died  out  during  or  soon  after  the  Mousterian 
period"  (Keith). 

Modern  representatives  of  Neandertal  man.  As  a  race, 
Homo  neandertalensts  is  surely  extinct.  Whether  or  not  his 
blood  has  entirely  vanished  from  the  earth  is  not  known,  for  in 
diverse  people,  as,  for  instance,  a  certain  Holland  strain,  the 
so-called  Old  Black  breed  of  the  Shetland  Islands,  and  again  in 
the  west  of  Ireland,  we  find  certain  Neandertal  characters  still 
prevalent,  but  not  all  of  them.  The  same  thing  is  also  true 
of  the  Australian  natives,  whose  physiognomy  is  often  very 
suggestive  of  the  Neandertals,  so  much  so  that  they  have  been 
held  by  certain  authors  to  be  persistent  representatives  of  that 
race.  But  while  many  individuals  show  one  or  more  of  the 
distinctive  characters,  no  one  individual  ever  possesses  all. 

Rhodesian  Man  {Homo  rhodesiensis) 

The  exact  place  of  the  interesting  relic  from  Broken  Hill 
mine,  northern  Rhodesia  (see  supra,  page  12),  is  yet  to  be 
established,  both  from  the  standpoint  of  antiquity  and  the 
position  that  it  holds  in  its  human  relationship.  The  preserved 
remains,  probably  complete  when  found,  by  the  workmen,  con- 


THE  ANTIQUITY  OF  MAN 


Fig.  8.    Homo  rhodesiensis.     Skull  and  face.    Adapted  in  part  from  Wood- 
ward.    Two  fifths  natural  size. 


sist  of  a  skull  with  a  part  of  the  lower  jaw,  both  so  perfect  that 
no  questionable  reconstruction  of  either  cranium  or  facial 
bones  need  be  made.  Certain  other  skeletal  elements  are  also 
present,  such  as  the  tibia  and  both  ends  of  the  femur,  the 
collar  bone,  part  of  the  scapula  and  of  the  pelvis.  Part  of  the 
upper  jaw  of  a  second  individual  was  found,  thus  establishing 
the  existence  of  a  race  or  tribe  as  against  an  aberrant  indi- 
vidual. 


30  THE  EVOLUTION  OF  MAN 

The  skull  is  not  fossilized,  except  that  its  animal  matter  has 
been  lost,  and  the  associated  animals  are  all  recent,  so  that  two 
of  our  criteria  of  age  fail  us  in  attempting  to  fix  other  than 
late  Pleistocene  or  even  the  Recent  period  for  the  time  when 
this  man  lived.  The  position  of  the  remains  in  a  cavern  is  not 
so  trustworthy  as  usual,  for  while  buried  under  tons  of 
mineralized  bones,  they  may  well  have  been  intruded  by  means 
of  a  shaft-like  cave. 

The  cranium  itself  is  not  remarkable,  either  for  its  form  or 
estimated  content,  which,  as  Keith  tells  us,  falls  between  a 
modern  English  and  an  ancient  French  (La  Chapelle)  skull. 
This  is  as  yet  an  estimate,  as  the  matrix  had  not  been  removed 
from  the  interior  of  the  skull  at  the  time  of  the  latest  pub- 
lished description.  We  are  therefore  at  present  ignorant  of 
any  especial  features  which  a  brain-cast  may  reveal.  Judging 
from  the  position  of  the  foramen  magnum,  the  head  was  well 
balanced  on  the  neck,  and  this,  together  wth  the  straight  shin 
and  the  character  of  the  ends  of  the  thigh  bone,  imply  a  fully 
erect  posture  in  no  sense  Neandertaloid. 

The  facial  region,  however,  departs  radically  from  what  we 
have  seen  in  that  it  shows  a  very  primitive  character  in  con- 
trast with  the  more  advanced  cranium.  The  brows  are  im- 
mensely prominent,  so  much  so  that  they  dwarf  the  forehead 
above  and  give  it  a  flattened  look  that  closer  scrutiny  does  not 
bear  out.  The  nose  was  broad  and  flattened  but  human,  and 
the  palate  so  broad  and  rounded  that  it  is  less  ape-like  than  in 
the  modern  negro.  The  lower  jaw  must  have  been  of  enor- 
mous strength  and  size  to  offset  it.  Smith  Woodward  tried 
the  Heidelberg  jaw  on  the  skull  but  found  it  too  short  and 
narrow.  The  Piltdown  jaw,  on  the  other  hand,  he  found  too 
large,  and  to  be  further  excluded  from  comparison  by  the 
prominent  canines  which  in  the  Rhodesian  man  are  not  dis- 
tinctively developed.  The  teeth  as  a  whole  are  strongly 
rooted,  although  badly  worn,  and  subjected  to  caries,  a  disease 


THE  ANTIQUITY  OF  MAN  31 

never  before  observed  in  a  prehistoric  skull  and  almost  un- 
known among  Englishmen  before  the  Roman  invasion.  The 
third  molar  or  wisdom  tooth  is  undergoing  reduction  as  in 
modern  man. 

As  one  views  the  Rhodesian  skull,  he  is  certainly  strongly 
impressed  with  its  Neandertal-like  appearance,  but  this,  as 
has  been  emphasized,  applies  to  the  face,  for  the  laterally 
compressed  instead  of  depressed  cranium,  together  with  the 
implied  erect  posture,  are  departures  in  the  more  modern 
direction.  It  would  seem  therefore  as  though  no  close  rela- 
tionship is  indicated  between  the  two  and  that  in  most  respects 
Rhodesian  man  is  much  more  advanced.  Certain  community 
of  food  adaptation  or  use  of  the  jaw  instead  of  other  means 
in  accomplishing  necessary  work,  may  account  for  the  facial 
similarities  which  in  the  Rhodesian  man,  as  in  that  of  Pilt- 
down,  may  well  have  lagged  behind  the  evolution  of  the  rest  of 
the  skull. 

Culturally,  Rhodesian  man  must  have  been  very  primitive, 
for  the  only  associated  implements  are  certain  rounded  pieces 
of  limestone  of  doubtful  utility,  although  the  crushed  skull  of 
a  lion-like  creature  found  in  association  is  indicative  of  a  cer- 
tain defensive  value. 

Homo  sapiens 

Upper  Paleolithic  man.  The  most  notable  of  the  several 
races  of  our  own  species  found  in  prehistoric  Europe  is  that 
of  Cro-Magnon,  in  almost  all  respects  the  most  perfect  man 
physically  that  has  come  within  our  knowledge.  The  first 
record  of  the  existence  of  this  race  was  found  at  Gower,  Wales, 
where  seventeen  skeletons  were  discovered  in  1852.  These, 
however,  were  lost  to  science  through  subsequent  burial  in  the 
village  cemetery.  Four  years  later  others  were  discovered  at 
Cro-Magnon,  France,  and  these  may  yet  be  seen  in  the  great 
Museum  of  the  Jardin  des  Plantes  in  Paris.    In  all  there  were 


32  THE  EVOLUTION  OF  MAN 

five  skeletons,  an  old  man,  a  woman,  a  child,  and  two  young 
men,  and  these  specimens  are  now  looked  upon  as  the  types  of 
the  race. 

The  most  impressive  thing  about  Cro-Magnon  man  is  the 
majestic  height,  which  averages  six  feet  one  and  five  tenths 
inches  in  the  young  men,  while  the  old  man  was  six  feet  four 
and  five  tenths  inches.  The  women,  on  the  other  hand,  had  an 
average  height  of  only  five  feet  five  inches,  but  little  above 
that  of  to-day.  The  limb  proportions  and  the  great  chest  are 
suggestive  of  negroes,  but  not  the  skull,  which  is  decidedly 
more  Asiatic  than  African  in  implied  affinities. 

The  skull  is  very  large,  even  the  female  brain  exceeding 
that  of  the  average  male  of  to-day.  This  is  perhaps  the  more 
significant,  since,  as  Keith  says,  the  size  of  the  body  has  a 
direct  influence  on  the  size  of  the  brain.  The  Cro-Magnon 
skull,  while  long  and  narrow,  is  entirely  modern,  lacking  as  it 
does  the  great  brow-ridges  of  his  predecessors.  Nor  is  the 
brain  in  any  way  distinctive  from  that  of  existing  man.  The 
face,  on  the  other  hand,  is  broad,  especially  across  the  cheek 
bones,  giving,  according  to  Osborn,  a  disharmony  of  face  and 
cranium.  The  facial  angle  is  equal  to  that  of  the  highest 
modern  man.     (See  Fig.  i  (Frontispiece)  and  Fig.  9.) 

The  jaw  is  strong  and  the  chin,  though  prominent,  is  narrow 
when  seen  from  in  front.  The  palate  is  also  narrow  and  the 
dental  arch  and  teeth  are  of  a  relatively  high  type. 

In  Obercassel,  near  Bonn,  Germany,  there  is  an  extinct  race 
resembling  very  closely  the  Cro-Magnons  except  for  a  short 
stature. 

Culturally,  these  late  Paleolithic  men  stood  very  high,  not 
only  in  their  production  of  flint  implements  of  Aurignacian 
type  (see  table,  page  4),  but  because  it  was  in  representa- 
tives of  this  race  that  primitive  art  found  so  high  and  so  very 
remarkable  an  expression.  This  art — sculpture,  engraving, 
and  painting — has  been  found  in  great  abundance  in  and  upon 


THE  ANTIQUITY  OF  MAN 


33 


Fig.  9.     Homo  sapiens    (Cro-Magnon  man).     Skull  and  face.     Adapted  in 
part  from  McGregor.     Two  fifths  natural  size. 


the  walls  of  caverns  in  the  Dordogne  region  and  in  the  Bas 
Pyrenees,  and  on  the  northern  coast  of  Spain.  A  detailed 
description  of  it  is  beyond  the  scope  of  this  essay,  and  the 
reader  is   referred  to   the   elaborately  illustrated  works  by 


34  THE  EVOLUTION  OF  MAN 

TAbbe  Breuil,*  Osborn,  and  others.  The  significance  of  this 
work,  whether  religious  or  merely  a  manifestation  of  an  artis- 
tic impulse,  is  not  at  all  clear.  That  the  great  bulk  of  the 
representations  were  of  animals  has  perhaps  some  bearing  on 
the  question;  at  all  events,  they  give  us  an  insight  into  the 
psychic  development  of  a  race  25,000  years  ago  fully  in  accord 
with  their  magnificent  physique. 

Among  other  types  of  Homo  sapiens,  more  or  less  con- 
temporaneous with  Cro-Magnon  man,  is  that  of  Grimaldi, 
of  which  the  typical  skeletons  come  from  the  famous  Grotte 
des  Enfants  near  Mentone  in  southern  France.  The  indi- 
viduals, a  woman  and  a  boy,  were  apparently  laid  on  the  floor 
of  the  cavern  and  protected  by  stone  blocks  over  which  in  the 
subsequently  accumulated  cave  earth  there  was  buried  a  typical 
Cro-Magnon  man.  The  Grimaldi  individuals  show  several 
features  which  have  been  interpreted  as  negroid, — long  nar- 
row crania,  flattened  nose  with  typical  nasal  gutters  at  the 
base,  protruding  teeth  and  slightly  retreating  chin,  and  palate 
and  teeth  like  those  of  the  Australians.  Although  the  lower 
limbs  are  disproportionately  long,  the  stature  was  low. 

Sollas  makes  much  of  this  occurrence,  together  with  the 
finding  of  steatopygous  figurines  in  adjacent  Mentone  caverns 
suggestive  in  their  conformation  of  characteristic  bodily  curva- 
tures of  the  modern  Bushmen.  He  therefore,  on  these  and 
other  data,  concludes  that  "Mentone  was  inhabited  at  the 
beginning  of  the  Aurignacian  age  by  a  race  allied  to  the  Bush- 
men." One  is  very  loath,  however  much  the  resemblances 
may  point  to  it,  to  attribute  the  glories  of  Aurignacian  art  to 
a  negroid  race,  in  the  presence  of  the  splendid  Cro-Magnons. 
The  Grimaldi  men  may  have  been  representatives  of  a  wave 
of  invasion  from  northern  Africa  which  spread  for  a  while 
into  Europe,  to  retreat  once  more  before  the  advance  of  the 

*  References  to  the  works  of  Breuil  may  be  found  in  the   bibliography  of 
Osborn's  "Men  of  the  Old  Stone  Age." 


THE  ANTIQUITY  OF  MAN  3s 

more  vigorous  Asiatics.  The  Cro-Magnon  race  has  also 
ceased  to  exist  as  such,  although  in  the  Dordogne  region, 
within  the  limits  of  their  ancient  home,  there  dwell  individuals 
which  possess  many  of  the  physical  traits  of  their  probable 
Aurignacian  ancestors.  We  have  to  go  to  Asia  to  the  region 
north  and  south  of  the  Himalayas  to  find  peoples  whose  facial 
characteristics  best  resemble  those  of  Cro-Magnon  man,  while 
the  stature  and  bodily  build  are  best  displayed  in  the  Sikhs. 
The  decline  of  the  Cro-Magnons,  Osborn  says  (19 16,  page 

450). 

may  have  been  due  partly  to  environmental  causes  and  the 
abandonment  of  their  vigorous  nomadic  mode  of  life,  or  it 
may  be  that  they  had  reached  the  end  of  a  long  cycle  of  psychic 
development.  .  .  .  We  know  as  a  parallel  that  in  the  history 
of  many  civilized  races  a  period  of  great  artistic  and  indus- 
trial development  may  be  followed  by  a  period  of  stagnation 
and  decline  without  any  apparent  environmental  causes. 

There  are  yet  a  number  of  remains  pertaining  apparently 
to  Homo  sapiens.  These  are  the  Galley  Hill  skull  in  the 
Thames  gravels,  and  the  remains  from  Dartford,  Clichy, 
Moulin  Quignon,  Crenelle,  Denise,  Olmo,  and  Castenedolo. 
All  of  these  have  been  in  dispute  as  to  their  antiquity,  prin- 
cipally because  of  their  very  modern  character.  But  Keith 
groups  them  collectively  under  the  head  of  pre-Mousterian 
man,  accepting  Galley  Hill,  Clichy,  and  Olmo  as  certainties, 
and  believes  that  they  may  well  be  cited  to  prove  the  great 
antiquity  of  our  own  species.  Other  competent  authorities, 
however,  consider  the  above  cited  as  "impossible  and  not 
proven."  Keith's  contention  is  that  Homo  sapiens  appeared 
at  a  remote  time,  flourished  for  a  while,  and  disappeared,  to 
be  replaced  by  the  more  primitive  but  not  ancestral  Neandertal 
man  of  Mousterian  time.  This  last  was  in  turn  deposed  from 
human  dominance  and  replaced  by  the  higher  race  again  in  the 
character  of  Cro-Magnon  man.    He  feels,  therefore,  that  the 


36 


THE  EVOLUTION  OF  MAN 


RECENT 


PLEISTOCENE 


PLIOCENE 


MIOCENE 


OLIGOCENE 


EOCENE 


Oranq 
{Simia) 


HOMINID/E 
Man 
Homo 
sapiens 

t 
H  sapiens 


5IMIID/E   {also  Simia) 


Gorilla 
(0  on  I  la) 


Chimpanzee         Gibbon 
(Pan)  {Hylobafes) 


Eoanthropus 
dawsoni 


Pithecanthropus 

t 


Pa/eosimia 


H.neanderthalensis 
H  heidelbergensis 


PJiopithecus 


Dryopithecus 


5/MUN/E 


i 


HYLOBATIN/E 


Propliopilhecus 

{!' Structural"  ancestor) 


Fig.  10.    Provisional  phylogeny  of  man  and  the  anthropoids. 
W.  K.  Gregory  1920   (1916). 


Modified  from 


divergence  of  the  primitive  stock  into  the  Neandertal,  Pilt- 
down,  and  sapiens  stems  occurred  early  in  the  Pliocene,  and 
that  the  differentiation  of  H.  sapiens  himself  into  the  four 
great  ethnic  groups,  African,  Australian,  Mongolian,  and 
European,  occurred  before  the  beginning  of  the  Pleistocene. 
On  this  account  he  is  perfectly  able  to  accept  a  Pleistocene  age 
at  least  for  the  men  of  the  New  World.  Back  of  the  Heidel- 
berg man,  the  European  record  is  blank,  unless  indeed  Pilt- 
down  and  Castenedolo  be  older.  The  last  particularly  Keith 
doubts. 

Tertiary  man.  Professor  Osborn  in  a  recent  number  of  the 
magazine.  Natural  History,  describes  at  some  length  beliefs 
which  he  holds  as  the  result  of  a  visit  to  East  Anglia  last 


THE  ANTIQUITY  OF  MAN  37 

summer.  That  visit  led  to  a  very  firm  conviction  of  the  pres- 
ence of  Upper  Pliocene  or  Tertiary  man  in  England,  as  shown 
by  his  cultures.  These  are  three,  two  of  which  ( i )  the  pre- 
Crag  industry  (rostro-carinate  flints)  of  Ipswich,  and  (2)  the 
Foxhall  flints  of  Ipswich,  are  placed  in  the  Upper  Pliocene, 
while  (3)  the  giant  flints  of  Cromer  are  considered  of  Lower 
Pleistocene  age. 

Supposedly  associated  with  the  Foxhall  flints  was  found  a 
human  jaw  which  unfortunately  cannot  now  be  located.  If 
it  could  be  found  and  the  certainty  of  association  determined, 
it  would  far  antedate  both  that  of  Piltdown  and  of  Heidelberg. 
The  figure  which  Osborn  published  of  this  jaw,  from  the 
original  by  Collyer  in  1867,  is  remarkable  in  that  it  is  the  jaw 
of  H.  sapiens,  if  correctly  drawn,  and  not  primitive  at  all  I 
But  this  is  exactly  what  Keith's  arguments  would  lead  us  to 
expect.  With  the  apparent  insufficiency  of  evidence,  however, 
judgment  as  to  the  antiquity  of  our  own  species  should  be  for 
the  present  withheld. 

Summary 

The  recorded  physical  changes  in  prehistoric  man  are : 

Increasing  cranial  capacity,  with  perfection  of  the  brain, 
especially  in  that  portion  which  is  concerned  with  the  higher 
intellectual  faculties  and  with  speech. 

Change  in  skull  conformation,  heightening  forehead,  and 
lessening  brow-ridges. 

Reduction  of  jaw  power  and  of  dental  arch,  which  results 
in  the  formation  of  the  chin  prominence. 

Changes  in  the  teeth,  such  as  reduction  of  canines  and  loss 
of  diastemata. 

Stature  increasing  and  becoming  more  erect,  although  the 
earliest  known  hominid.  Pithecanthropus,  was  fully  upright, 
pointing  to  great  antiquity  for  this  characteristic. 


38  THE  EVOLUTION  OF  MAN 

As  yet  there  is  no  actual  connection  with  ape-like  forms 
ancestral  to  both  the  modern  apes  and  man,  but  the  table  here 
reproduced  (Fig.  lo)  gives  a  tentative  view  of  implied  rela- 
tionships. Exploration  in  Asia  now  being  carried  forward 
under  the  auspices  of  the  American  Museum  of  Natural  His- 
tory will,  it  is  hoped,  yield  additional  light  on  the  problem  of 
human  origins,  for  all  of  our  evidence  points  to  central  Asia 
as  the  birthplace  of  mankind,  and  to  the  Miocene,  1,000,000 
to  2,000,000  years  ago,  as  the  time  of  his  origin. 

The  antiquity  of  man  has  thus  been  made  known  by  direct 
evidence  in  the  form  of  human  relics,  the  greatest  age  of  which 
can  hardly  be  less  than  half  a  million  years.  Corroborative 
evidence  lies  in  the  great  variation,  not  alone  between  the 
several  species  of  prehistoric  man,  but  also  among  the  many 
races  of  Homo  sapiens  himself,  of  which  Gregory  recognizes 
twenty-six,  with  a  number  of  sub-races.  And  that  the  major 
divisions  are  very  old  is  attested  by  ancient  murals  and  other 
documents  of  the  Egyptians  and  other  oriental  peoples. 

Man's  distribution  is  world-wide.  In  these  days  of  easy 
travel,  this  is  not  so  significant  as  it  was  in  the  ancient  days 
when  dispersal  meant  slow  tribal  migrations  sometimes  cover- 
ing generations  of  time. 

The  intelligence  of  man  so  far  surpasses  that  of  his  nearest 
competitors,  the  anthropoids,  that  the  mental  gulf  between 
them  is  immeasurable,  while  the  moral  and  spiritual  attributes 
of  mankind  were  also  long  in  the  making. 

Communal  Hfe,  as  contrasted  with  the  much  more  common 
herding  instinct  of  the  gregarious,  has  been  attained  but  twice, 
among  the  social  insects  and  among  men.  A  long  period  of 
time  is  again  necessary  for  this  attainment. 

Finally,  man's  remains,  or  the  products  of  his  industry,  are 
found  associated  with  numerous  extinct  creatures,  of  which  he 
alone  survives. 


CHAPTER  II 
THE  NATURAL  HISTORY  OF  MAN 

HARRY  BURR  FERRIS 

E.   K.   HUNT  PROFESSOR  OF  ANATOMY,  YALE    UNIVERSITY 

The  fundamental  structural  unit  in  man  and  other  organ- 
isms is  a  microscopic  mass,  called  a  cell,  which  varies  consider- 
ably in  shape  and  size,  and  possesses  a  central  spherical  body, 
termed  the  nucleus.  Animals  composed  of  a  single  cell  are 
called  protozoa,  those  made  of  many  cells,  metazoa.  Man  is 
a  metazoan  and  it  has  been  estimated  that  his  body  is  com- 
posed of  more  than  twenty-six  trillion  cells.  Animals  without 
a  longitudinal,  dorsal  body  axis  are  called  invertebrates  while 
those  with  such  an  axis  are  known  as  vertebrates.  Man  has 
such  an  axis  and  also  possesses  other  characters  common  to 
the  vertebrates,  such  as  a  bony  cavity,  dorsal  to  the  body  axis, 
for  the  hollow  central  nervous  system,  and  also  an  internal, 
segmented  skeleton  as  shown  in  the  serial  repetition  of  ribs 
and  vertebrae.  Man  is  also  a  mammal  in  that  he  possesses 
mammary  glands  and  hair  and  has  the  thoracic  cavity,  contain- 
ing the  heart  and  lungs,  separated  from  the  abdominal  cavity 
by  a  complete  diaphragm.  Because  of  structural  similarities 
he  belongs  to  the  order  of  primates  together  with  the  lemurs, 
monkeys,  and  apes. 

Structurally  man  differs  from  his  nearest  relatives,  the  an- 
thropoid apes,  by  differences  of  degree  rather  than  of  kind 
such  as  the  better  adaptation  of  his  feet  and  vertebral  column 
to  the  upright  position,  the  non-opposability  of  the  great  toe, 


40  THE  EVOLUTION  OF  MAN 

the  greater  size  of  the  cranium  and  the  brain,  the  relatively 
smaller  and  less  projecting  face,  and  the  relatively  and  abso- 
lutely longer  lower  extremities.  Man  does  not  differ  much 
more  from  the  tailless  apes,  like  the  gorilla,  than  they  differ 
from  the  old-world  tailed  apes. 

Anthropologists  generally  agree  that  living  man  is  repre- 
sented by  one  genus  Homo  and  a  single  species  sapiens,  and 
that  the  various  races  are  merely  varieties  of  Homo  sapiens. 
Fossil  remains  of  man  have  been  found,  as  has  been  explained 
in  the  previous  chapter,  which  represent  several  other  species 
and  which  show  marked  ape-like  characters.  It  is  not  certainly 
known  whether  present  man  has  evolved  through  these  fossil 
forms  or  whether  they  rather  represent  collateral  lines  now 
extinct. 

The  races  differ  notably  in  many  parts  of  their  bodies.  The 
most  important  differences  are  shown  in  the  size  and  form  of 
the  head,  in  the  skeletal  and  physiognomic  characters,  in  the 
color  of  the  skin,  the  form  and  color  of  the  hair,  and  the  body 
proportions.  There  are  also  differences  in  the  susceptibility 
to  disease  and,  although  less  marked,  psychic  differences 
in  the  races,  particularly  as  exhibited  in  the  temperament. 
The  soft  tissues  likewise  show  racial  differences  although  little 
in  regard  to  them  is  known.  This  subject  offers  a  large  field 
for  further  investigation.  It  is  possible  also  that  the  races 
differ  in  protein  reactions  and  hormones,  as  held  by  some  au- 
thorities, a  subject  as  yet  quite  unexplored. 

Blumenbach's  classification  of  the  races  is  as  satisfactory 
as  any,  although  the  use  of  a  single  criterion  of  race  distinc- 
tion, namely,  skin  color,  is  open  to  objection.  Blumenbach 
classifies  the  races  as  follows :  ( i )  Caucasian,  having  a  white 
skin,  (2)  Mongolian,  having  an  olive  skin,  (3)  Ethiopian, 
having  a  black  skin,  (4)  American,  having  a  dark  skin  with 
more  or  less  of  a  red  tint,  (5)  Malay,  having  a  brown  or 
tawny  skin.     Some  classifications  include  the  Australians  as  a 


I 


THE  NATURAL  HISTORY  OF  MAN  41 

separate  race.  Additional  Interest  Is  given  to  this  classification 
of  the  races  as  It  corresponds  In  a  general  way  to  their  geo- 
graphic distribution  as  shown  in  Fig.  2. 


B 


Fig.  11.  Diagram  showing  the  fertilization  of  the  ovum.  A,  the  mature 
ovum  with  a  central  nucleus,  or,  as  it  is  termed,  female  pronucleus  (e), 
containing  the  reduced  number  of  chromosomes;  the  others  have  been  given 
off  into  the  first  and  second  polar  bodies  (a  a').  A  single  sperm  (b)  is 
entering  the  ovum.  B,  later  stage  in  which  the  male  pronucleus  (d),  with 
the  two  paternal  chromosomes,  has  formed  from  the  sperm.  The  sperm 
also  brings  to  the  ovum  the  centrosome  (c)  which  is  regarded  as  the  dynamic 
division  center.  C,  still  later  stage  in  which  the  male  and  female  pronuclei 
are  uniting  to  form,  in  stage  D,  the  segmentation  nucleus  (e')  which  contains 
an  equal  amount  of  maternal  and  paternal  chromatin.  Following  this  the 
fertilized  egg  cell  will  divide  by  the  complicated  process  of  mitosis  which 
insures  the  equal  division  of  the  chromatin  material  among  the  daughter 
cells,  a,  first  polar  body  (divided  into  two  parts);  a',  second  polar  body; 
b,  sperm  entering  the  ovum;  c,  centrosome  (later  divides);  d,  male  pro- 
nucleus; f,  cell  wall;  g,  body  of  cell.    Redrawn  from  Cunningham,  Anatomy. 


42  THE  EVOLUTION  OF  MAN 

Early  Prenatal  Development 

Reproduction  is  started  by  the  union  of  the  germinal  cells 
of  the  two  sexes  (Fig.  ii).  These  cells  are  differentiated  in 
development  before  the  sixth  week  of  prenatal  life  and  set 
aside  in  special  organs,  the  gonads,  for  the  perpetuation  of 
the  race.  Even  at  this  early  period  the  sex  of  the  germinal 
cells  of  the  embryo  is  structurally  indicated.  The  female  cell, 
or  ovum,  is  spheroidal  in  shape  and  although  it  is  one  of  the 
largest  cells  of  the  body  yet  it  is  sa  small  as  to  be  hardly 
visible  to  the  naked  eye.  The  male  cell,  or  sperm,  is  very 
much  smaller  even  than  the  ovum  and  is  elongated  and 
specialized  for  active  motility.  Both  the  sperm  cells  and  the 
ova  during  their  development  go  through  a  series  of  changes 
which  result  in  the  reduction  to  one  half  of  the  chromatin 
material  contained  in  the  nucleus.  This  is  an  important  fact 
as  the  chromatin  is  regarded  as  the  carrier  of  the  hereditary 
qualities,  and  the  fusion  of  these  two  cells  at  the  time  of  fertili- 
zation, each  with  one  half  the  normal  amount  of  chromatin, 
produces  again  a  complete  cell  with  the  typical  amount  of 
chromatin  and  having  an  equal  proportion  of  maternal  and 
paternal  hereditary  substance.  As  a  result  of  fertilization  the 
egg  cell  has  the  power  of  almost  indefinite  multiplication  and 
the  still  more  marvelous  power  of  differentiation  so  that  its 
descendants  are  not  all  alike,  but  some  form  nerve  cells,  others 
gland  cells,  still  others  muscle  cells,  et  cetera.  This  differentia- 
tion in  structure  is  accompanied  also  by  a  corresponding  func- 
tional differentiation.  It  may  be  possible  to  explain  many  of 
the  processes  of  life  on  the  mechanistic,  or  physico-chemical 
basis,  but  it  is  difficult  at  present  to  explain  reproduction  on 
this  theory. 

After  fertilization,  the  repeated  multiplication  of  the  egg 
cell  quickly  produces  a  solid  spherical  mass  of  similar  cells, 
still  almost  microscopic  in  size,  called  the  morula.  Some  of  the 
cells  soon  become  massed  on  one  side  and  in  this  region  two 


I 


B 


Ectoderm 


Amniotic  cavity 

Ccelom 
Trophectoderm 
Archenterofi' 
Entoderm 

Mesoderm 


..•.»;:••• 


Ectoderm  of  embryo 


Ectoderm  of  amnion 


Allantois 


D 

Body  stalk 


imniotic  cavity 

Trophectoderm 

Yolk  sac 
Entoderm 

Splanchnic 
fuesoderm 
Extra-embry- 
onic ccelom 


Chorionic  meso- 
derm 
Trophoderm 


Ectoderm  of  embryo 
Cavity  of  amnion 
Mesoderm  of 
amnion 
Ectoderm  of 
chorion 
Cavity  of  yolk 
sac 
Entoderm  of 
yolk  sac 
Mesoderm 
of  yolk  sac 
Extra-embry- 
onic ccelom 


Mesoderm, 
of  chorion 

Chorionic  villi 


Fig.  12.  Four  diagrams  of  early  human  embryos  (based  on  figures  of  Robinson  and 
Minot).  A,  Hypothetical  Stage;  B,  Bryce-Teacher  Embryo  (modified);  C,  Peter's 
Embryo;  D,  Graf  Spee's  Embryo.  From  Prentiss  and  Arey,  Embryology.  By  permission 
of  W.  B.  Saunders  and  Co. 


THE  NATURAL  HISTORY  OF  MAN  43 

cavities  develop  (Fig.  12),  one  becomes  the  amniotic  cavity 
and  ultimately  surrounds  the  embryo,  and  the  other  forms  the 
yolk  sac,  part  of  which  eventually  becomes  the  alimentary 
canal.  Some  of  the  cells  of  the  two  sacs,  which  lie  adjacent 
and  are  destined  to  develop  the  embryo,  form  two  layers, 
known  as  the  ectoderm  and  endoderm,  or  the  external  and 
internal  membranes.  This  structural  arrangement  represents 
the  earliest  stage  known  in  man's  development,  the  previous 
stages  described  above  being  hypothetical  and  based  on  obser- 
vations made  on  the  developing  eggs  of  other  mammals. 
Later,  through  the  multiplication  of  the  ectoderm  cells  an 
elongated  area,  known  as  the  primitive  streak,  is  formed  and 
this  indicates  the  anteroposterior  axis  of  the  embryo. 

Along  this  primitive  streak,  between  the  outer  ectoderm  and 
the  inner  endoderm  layers,  a  third  layer  is  produced,  known 
as  the  mesoderm.  We  now  have  in  the  region  where  the  em- 
bryo is  developing,  known  as  the  embryonic  area,  three 
layers  of  cells,  each  having  its  own  distinctive  characteristics. 
These  are  known  as  the  primary  germ  layers,  and  from  them 
all  the  organs  and  parts  of  the  body  are  later  derived.  In  the 
human  embryo  all  of  the  organs  are  formed  by  the  third  month 
of  development.  From  the  outer  layer,  or  ectoderm,  are 
formed  the  outer  layer  of  the  skin,  or  epidermis,  including  its 
various  appendages  such  as  the  hair  and  sweat  glands,  the  cells 
lining  the  mouth,  the  enamel  of  the  teeth,  and  the  entire 
nervous  system  including  the  sensory  portions  of  the  sense 
organs.  From  the  middle  layer,  or  mesoderm,  are  formed  the 
skeleton  and  other  supporting  tissues  and  the  muscles,  the 
vascular  system,  and  the  sex  cells.  From  the  innermost  layer, 
or  endoderm,  are  developed  the  cells  lining  the  alimentary 
canal  and  the  essential  secreting  cells  of  the  various  organs 
which  develop  as  outgrowths  from  it,  such  as  the  thyroid 
gland  in  the  neck,  the  lungs,  the  liver,  and  the  pancreas.  In 
general  it  may  be  said  that  the  endoderm  supplies  the   all- 


44  THE  EVOLUTION  OF  MAN 

mentary  system;  the  mesoderm,  the  locomotor  apparatus,  and 
the  sex  cells  for  the  preservation  of  the  race;  and  the  ecto- 
derm, the  nervous  system  which  is  placed  in  control  of  the 
body  and  puts  man  in  touch  with  his  environment.  This 
method  of  development  is  essentially  similar  in  other  animals. 

Up  to  this  point  the  embryo  appears  as  a  rather  simple 
multicellular  animal  of  the  invertebrate  type.  The  first  indi- 
cation that  it  is  to  become  a  vertebrate  is  the  development  of 
a  dorsal,  longitudinal,  rod-like  axis,  called  the  notochord, 
which  eventually  extends  posteriorly  from  the  base  of  the 
brain  through  the  length  of  the  body.  In  the  lowest  forms  of 
aquatic  vertebrates  this  is  the  only  longitudinal  supporting 
axis  the  body  ever  possesses,  but  in  the  higher  fishes  and  the 
terrestrial  vertebrates,  where  a  more  stable  axis  is  necessary, 
the  notochord  is  replaced  by  a  more  rigid,  segmented,  bony 
structure,  the  vertebral  column. 

The  rudiment  of  the  nervous  system  now  appears,  anterior 
to  the  primitive  streak  and  dorsal  to  the  notochord,  as  a  longi- 
tudinal groove,  known  as  the  neural  groove  (Fig.  13),  in  the 
dorsal  surface  of  the  thickened  ectoderm.  The  lateral  edges 
of  the  groove  become  elevated  and  meet  and  fuse  above  it 
in  the  mid-dorsal  line  and  thus  form  a  hollow,  ectodermal  tube, 
called  the  neural  tube.  Practically  the  entire  nervous  system  is 
developed  from  the  cellular  walls  of  this  structure.  Shortly 
afterwards  a  part  of  the  yolk  sac  lying  under  the  embryo  is 
folded  of{  and  this  process  results  eventually  in  the  formation 
of  an  endodermal  tube  under  the  notochord  which  is  the  rudi- 
ment of  the  alimentary  canal  (Fig.  12  D). 

Also  the  mesoderm,  which  at  this  stage  is  to  be  found  lying 
along  each  side  of  the  neural  canal,  becomes  cleft  transversely, 
beginning  first  just  behind  the  brain,  and  this  results  in  the 
formation  of  a  linear  series  of  segments,  or  myotomes  (Fig. 
14),  extending  the  length  of  the  body  of  the  embryo.  This 
primitive  segmentation  persists  in  a  modified  form  in  adult 


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THE  NATURAL  HISTORY  OF  MAN  45 

man  in  the  serial  arrangement  of  the  vertebrae,  the  ribs,  and 
the  spinal  nerves.  In  the  lateral  mesoderm  a  cavity  develops 
which  is  the  beginning  of  the  body  cavity,  or  coelom,  and 
later  contains  the  heart,  lungs,  and  viscera  of  the  abdomen. 
This  cavity  splits  the  mesoderm  into  two  layers.  The  outer 
layer  joins  with  the  ectoderm  to  form  the  body  wall,  and  the 
inner  layer  with  the  endoderm  to  form  the  wall  of  the  ali- 
mentary canal  which  in  time  becomes  entirely  enclosed  by  the 
mesoderm  and  ectoderm  of  the  body  wall.  The  human 
embryo  at  this  stage  has  acquired  the  characteristics  of  a  typi- 
cal vertebrate. 

Later  Prenatal  Development 
The  Nervous  System.  The  hollow  neural  tube  early  ex- 
pands at  its  anterior  end  into  three  sacs  (Fig.  15),  the  primary 
cerebral  vesicles,  or  as  they  are  often  called  the  fore-,  mid-, 
and  hind-brain,  and  later  the  first  and  third  sacs  partially  sub- 
divide making  altogether  ^Yt  enlargements.  From  the  walls 
of  these  five  sacs  and  from  the  remainder  of  the  neural  tube 
are  developed  all  parts  of  the  brain  and  spinal  cord  and  nearly 
all  parts  of  the  cranial  and  spinal  nerves  which  run  to  the 
peripheral  regions  of  the  head  and  body.  The  developing 
brain  increases  in  length  rapidly  and  bends  in  three  places,  the 
cervical  flexure  remaining  permanently.  A  small  sac  grows 
out  on  each  side  of  the  hollow  anterior  brain  vesicle  and  ulti- 
mately forms  the  retina  of  the  eye  (Fig.  15),  which  is  thus  a 
part  of  the  brain  projected  to  the  surface  of  the  head  so  the 
light  can  reach  it.  By  thickenings,  thinnings,  and  outgrowths, 
in  different  parts  of  the  walls  of  the  cerebral  sacs,  and  by  the 
development  of  myriads  of  nerve  cells  and  fibers  growing  in 
many  directions,  the  various  parts  of  the  brain  are  ultimately 
formed.  Another  sac  grows  out  from  each  side  of  the  fore- 
brain  in  front  of  the  developing  retina  which  (Fig.  15),  in 
man  especially,  possesses  the  power  of  extensive  growth.  This 
sac  expands  in  all  directions  but  especially  backward,  spreading 


46  THE  EVOLUTION  OF  MAN 

over  the  rest  of  the  brain  tube,  and  ultimately  forming  the  cere- 
brum, which  is  so  large  in  man  in  comparison  with  the  lower 
animals.  All  of  this  sac,  except  the  lower  part,  as  well  as  the 
parts  of  the  adult  brain  formed  from  it,  is  known  as  the  mantle, 
or  pallium  (Fig.  i6),  the  olfactory  portion  of  which  is  the 
archipallium  since  in  evolution  it  is  the  oldest  part  of  the  brain, 
while  the  rest,  being  a  more  recent  addition,  is  called  the  neo- 
pallium. The  latter  is  most  extensively  developed  in  man 
and  forms  the  major  part  of  the  cerebrum. 

The  early  condition  of  the  neopallium  in  man  represents 
about  the  extent  of  the  pallium  in  the  adult  fish  (Fig.  i6). 
As  it  grows  further  backward  it  represents  first  the  extent  of 
the  pallium  in  the  next  higher  class  of  vertebrates,  the  amphib- 
ians, and  later  the  extent  in  reptiles.  Finally,  as  it  begins  to 
cover  the  cerebellum,  we  have  the  extent  of  the  pallium  as 
found  in  lower  mammals  and  when  it  covers  the  cerebellum 
completely  we  have  the  human  pallium.  Thus  we  see  that  the 
pallium  in  its  development  in  man  passes  through  successively 
the  various  stages  represented  in  the  adult  forms  of  the  dif- 
ferent vertebrates,  starting  with  the  fish  and  terminating  with 
the  mammalian  type  (Fig.  i6).  Similarly  the  structural  unit 
of  the  nervous  system,  the  nerve  cell,  or  neurone  (Fig.  17), 
passes  in  its  development  in  man  from  the  very  simple  neurone 
of  the  fish  through  the  increasingly  complex  forms  of  the  vari- 
ous vertebrates  to  its  greatest  complexity  in  man. 

The  sensory  nerves  ( Fig.  18),  which  connect  the  skin  and 
the  various  peripheral  sense  organs  to  the  central  nervous  sys- 
tem, develop  by  a  separation  of  serial  groups  of  cells  from  the 
dorsal  portion  of  the  neural  folds.  From  each  of  the  cells  in 
these  groups  two  processes  grow  out.  One  grows  into  the 
central  nervous  system  and  the  other  pushes  its  way  among 
the  cells  of  the  embryo  until  it  reaches  the  sensory  structures 
at  the  periphery.  The  motor  nerves  (Fig.  18)  which  control 
the  muscles,  on  the  contrary,  grow  out  from  cells  situated  in 


Diencephalon 


Mesencephalon 


Cephalic 
flexure 


B 

Thalamus 


Optic 
cup 
Pontine  flexure 


Myelencephalon 


Pallium 


Mesencephalon 


Meten- 
cephalon 
Corpus  striatum 
Optic  recess 

Hypothalamus 


Medulla  oblongata 


Fig.  15.  Developing  brain  from  a  7  mm.  human  embryo  showing  the  vesicles. 
A,  lateral  view;  B,  median  sagittal  section.  The  fore-brain  consists  of  the  telen- 
cephalon (region  labelled  pallium)  and  diencephalon;  the  mid-brain  consists  of  the 
mesencephalon,  and  the  hind-brain  of  the  metencephalon  (cerebellum)  and 
myelencephalon  (medulla  oblongata).  The  portion  of  the  fore-brain  which 
becomes  the  retina  of  the  eye  is  indicated  in  A  as  the  optic  cup.  From  Prentiss  and 
Arey,  Embryology.     By  permission  of  W.  B.  Saunders  and  Co, 


THE  NATURAL  HISTORY  OF  MAN  47 

the  anterior  part  of  the  spinal  cord  and  thread  their  way 
among  the  embryonic  cells  till  they  reach  the  proper  muscle, 
where  they  break  up  Into  fine  fibrils  which  become  embedded  In 
its  fibers.  Nerve  fibers,  therefore,  are  merely  the  very  elon- 
gated processes  of  nerve  cells.  How  these  fibers  are  directed 
to  their  proper  terminations  among  the  myriads  of  cells, 
whether  by  chemical  attraction  or  other  force,  and  so  seldom 
go  astray,  has  never  been  determined. 

Before  the  nerves  function  they  become  surrounded  by  a 
translucent  covering,  called  the  myelin  sheath,  which  Is  as- 
sumed at  different  periods  during  development.  In  the  various 
parts  of  the  spinal  cord  and  brain.  In  general  the  myelin 
sheaths  are  assumed  first  by  the  peripheral  sensory  and  motor 
nerves,  thereby  completing  the  reflex  mechanism  which  In  man 
occurs  at  about  the  sixth  month  of  prenatal  life.  Following 
this  the  different  groups  of  cells  in  the  spinal  cord  are  asso- 
ciated by  the  development  of  the  myelin  sheaths  on  the  con- 
necting nerves,  thus  arranging  for  association  of  the  reflex 
actions.  Still  later  the  nerves  connecting  the  spinal  cord  with 
the  cerebellum  myelinate,  thus  completing  the  mechanism  for 
coordination  of  movements.  Then  the  afferent  nerves,  which 
connect  the  spinal  cord  with  the  brain,  assume  their  myelin 
sheaths,  thus  preparing  the  pathway  for  sensory  impressions. 
Not  until  after  birth,  however,  are  the  efferent  tracts  connect- 
ing the  cerebrum  and  spinal  cord  myelinated,  thus  placing  the 
cerebrum  In  control  of  the  parts  below  and  completing  the 
motor  pathway.  This  late  completion  of  the  motor  tracts  in 
man  explains  the  great  helplessness  of  the  human  Infant  at 
birth,  a  condition  which  is  in  striking  contrast  to  that  In  many 
of  the  lower  animals.  It  Is  believed  that  the  assumption  of  the 
myelin  sheaths  in  the  various  association  tracts  of  the  cerebrum 
continues  during  the  period  of  growth  and  perhaps  until  forty 
years  of  age.  As  no  brain  cells  are  ever  formed  after  birth, 
the  increasing  myellnation  of  the  nerve  fibers  is  the  chief  struc- 


48  THE  EVOLUTION  OF  MAN 

tural  change  in  the  brain  that  can  be  correlated  with  the  educa- 
tional process. 

The  Eye.  The  eye  develops  from  three  sources.  The 
retina,  as  noted  above,  is  a  direct  outgrowth  from  the  fore- 
brain  on  the  side  of  the  head.  The  lens  is  an  ingrowth  from 
the  ectoderm,  and  the  sclerotic  and  choroid  membranes,  which 
form  protective  coverings  enclosing  the  retina,  are  mostly  dif- 
ferentiated from  the  mesoderm.  Up  to  the  sixth  month  of 
prenatal  life  a  membrane  stretches  across  the  pupil  of  the  eye 
which  sometimes  fails  to  disappear  and  thus  causes  blindness. 
Also  the  eyelids  are  grown  together  until  about  the  same 
period,  but  in  man,  unlike  the  condition  in  certain  other 
animals,  such  as  kittens,  a  separation  of  the  lids  occurs  before 
birth. 

The  Ear.  The  Internal  ear  forms  as  a  saccular  ingrowth 
from  the  ectoderm  on  the  side  of  the  head.  This  invaginated 
sac  becomes  greatly  modified  but  eventually  forms  the  semicir- 
cular canals,  which  preside  over  the  function  of  equilibrium, 
and  the  highly  developed  cochlea  which  is  concerned  with  hear- 
ing. The  internal  ear  is  regarded  as  a  specialization  of  a  part 
of  the  lateral  line  sensory  organs  of  the  lower  vertebrates, 
which  in  the  fish  is  concerned  with  balancing  and  movement 
only.  The  added  cochlea,  which  is  present  in  terrestrial 
animals,  forms  the  organ  of  hearing. 

Alimentary  Canal.  The  alimentary  canal,  as  stated  above, 
is  early  folded  off  from  the  yolk  sac  as  a  tube  lying  under  the 
notochord  of  the  embryo.  Both  ends  of  the  tube  are  closed  for 
a  time,  but  long  before  birth  an  anterior  and  posterior  connec- 
tion with  the  external  surface  of  the  embryo  has  been  made. 
At  the  anterior  end  of  the  body  on  each  side  of  the  neck,  four 
crevices  (Fig.  14)  appear  in  the  early  embryo  which,  in  the 
lower  vertebrates  such  as  the  fish,  open  directly  into  the 
pharyngeal  region  of  the  alimentary  canal  and  form  the  gill 
clefts.     In  man,  however,  these  crevices  never  go  on  to  the 


£:      6IR0 


Fig.  16.  The  pallium  and  cerebellum,  in  the  brains  of  various  vertebrates.  The  cerebellum 
is  in  black.  After  Edinger.  From  Bailey  and  Miller,  Embryology.  By  permission  of  William 
Wood  and  Co. 


THE  NATURAL  HISTORY  OF  MAN  49 

formation  of  gill  clefts  but  soon  disappear.  Their  presence, 
however,  is  indicative  of  a  fish  stage  in  his  development.  The 
lungs,  which  are  the  permanent  respiratory  organs  (Fig.  19) 
of  man,  are  developed  from  the  upper  end  of  the  alimentary 
canal  by  the  formation  of  a  single  hollow  sac.     This  later 

Han 


Frog 


L/^at^c^ 


Rat 


Ei/o/utior) 
of  ^he 
net'v'e  ce// 


Oeyv/o/omenf 
of  net^ye  ce// 


Fig.   17.     The  individual   and  evolutionary  development  of  the  nerve  cell. 
After  Cajal.     Redrawn  from  Donaldson,   The  Groivth  of  the  Brain. 


bifurcates  to  form  the  rudiments  of  the  right  and  left  lungs  and 
these  by  repeated  branching  develop  the  highly  ramified,  tubu- 
lar structure  of  the  adult  lungs.  The  early  simple,  sac-like 
lung  of  the  human  embryo  Is  similar  in  structure  to  the  per- 
manent, saccular  lung  of  the  adult  amphibians. 

From  the  neck  region  of  the  alimentary  tube,  three  other 
organs  develop  as  branching  outgrowths,  all  of  which  finally 
form  organs  of  internal  secretion,  namely  the  thyroid,  the 


so  THE  EVOLUTION  OF  MAN 

parathyroid,  and  the  thymus  glands  (Fig.  19).  Another  im- 
portant endocrine  organ,  the  pituitary  body,  or  hypophysis, 
has  a  double  origin  In  that  a  portion  of  It  develops  as  an 
upgrowth  from  the  ectoderm  which  lines  the  extreme  anterior 
end  of  the  alimentary  canal,  or  buccal  cavity,  and  another  por- 
tion, which  fuses  with  the  former,  develops  as  a  downgrowth 
from  the  brain.  These  glands,  through  their  Internal  secre- 
tions, or  hormones.  Influence  development  In  various  ways. 
All  of  them  ultimately  lose  their  connection  with  the  ali- 
mentary canal.  The  thyroid  gland  moving  down  the  ventral 
side  of  the  neck  stops  just  above  the  thorax.  The  thymus, 
which  in  the  calf  is  commonly  called  the  sweetbread,  descends 
into  the  thorax  until  it  lies  just  above  the  heart.  Early  In  pre- 
natal life  the  glandular  structure  of  the  thymus  disappears  and 
a  lymphoid  tissue,  such  as  we  find  In  the  tonsils,  takes  Its  place. 
This  organ  continues  to  grow  until  the  child  is  about  two  years 
of  age  and  then  gradually  diminishes  in  size,  disappearing  at 
about  twenty  years  of  age.  This  same  remarkable  history  of 
the  thymus  is  found  in  other  mammals  as  well  as  in  man.  Little 
is  known  definitely  with  regard  to  the  function  of  this  organ. 

Lower  down  the  ahmentary  canal,  just  below  the  spindle- 
shaped  enlargement  which  represents  the  developing  stomach, 
two  other  organs  grow  out  and,  by  repeated  branching,  form 
the  liver  and  pancreas  (Fig.  19) .  These  always  remain  In  con- 
nection with  the  alimentary  canal  by  ducts  which  carry  their 
secretions.  The  pancreas  develops  as  two  outgrowths  which 
fuse.  Usually  only  one  of  the  ducts  persists.  Occasionally 
it  is  found  In  man  that  both  persist  and  the  pancreas  pours  its 
secretion  into  the  intestine  by  two  ducts  Instead  of  one.  The 
explanation  of  such  cases  undoubtedly  lies  In  the  double  origin. 

The  Vascular  System.  The  heart  differentiates  from  a  por- 
tion of  the  mesoderm  lying  underneath  the  pharynx  in  the  head 
region  of  the  embryo.  Two  straight  tubes  are  first  formed 
(Fig.  20).    These  quickly  fuse  for  part  of  their  length  form- 


Fig.  18.  Transverse  section  through  the 
spinal  cord  of  a  76-hour  chick  embryo 
showing  the  early  development  of  a  spinal 
nerve.  After  Cajal.  A,  motor  root;  B, 
sensory  root;  C,  bifurcation  of  fibers  of 
sensory  root,  a,  b,  c,  d,  neurones  in  various 
stages  of  differentiation.  From  Bailey  and 
Miller,  Embryology.  By  permission  of 
William  Wood  and  Co. 


THE  NATURAL  HISTORY  OF  MAN  51 

ing  a  single  tube  which  is  bifurcated  at  each  end.  At  this  stage 
of  development,  the  human  heart  resembles  that  found  in  the 
adult  of  the  lowest  vertebrates.  Later  the  single  tube  of  the 
developing  heart  partially  subdivides  into  two  cavities,  the 
auricle  and  the  ventricle,  and  it  now  resembles  the  heart  of 
the  adult  of  the  next  higher  vertebrates,  the  fish.  The  auricle 
IS  then  subdivided  Into  two  cavities,  and  the  human  heart  of 
three  cavities  resembles  the  fully  developed  heart  of  the  next 
higher  vertebrate,  the  amphibian.  Later  the  ventricle  Is  sub- 
divided and  the 'human  heart  contains  four  cavities,  which  is 
characteristic  of  the  adult  heart  of  the  highest  vertebrates. 
Thus  It  Is  evident  that  the  human  heart  In  Its  development 
passes  through  stages  representing  the  different  adult  stages 
of  the  various  ascending  vertebrate  classes.  This  again  is  an 
illustration  of  the  so-called  Law  of  Recapitulation,  which  holds 
in  essence  that  man  in  his  individual  development  repeats  the 
evolutionary  history  of  the  race,  or  that  "ontogeny  repeats 
phylogeny.'^ 

The  blood  vessels,  consisting  of  the  arteries,  capillaries,  and 
veins,  are  tubes  which  differentiate  from  the  mesoderm  cells 
in  all  parts  of  the  body  and  become  connected  with  the  heart. 
The  blood  cells,  which  are  present  In  countless  numbers  In  the 
blood,  likewise  are  derived  from  mesoderm  cells,  and  we  find 
that  the  red  blood  cells  of  the  human  embryo  when  first  formed 
are  large  and  nucleated.  In  this  stage  they  resemble  those 
of  the  fishes  and  amphibians;  later  their  structure  is  similar  to 
those  of  the  reptiles.  Finally,  before  birth,  they  become  In 
man,  as  In  all  mammals,  non-nucleated  and  biconcave. 

The  complete  natural  history  of  the  human  red  blood  cor- 
puscles has  never  been  learned.  It  Is  known  that  they  are  con- 
stantly formed  In  the  adult  from  the  cells  of  the  red  marrow 
In  the  ends  of  the  long  bones  and  that  they  are  nucleated  at 
first  but  lose  their  nuclei  before  they  enter  the  circulation. 
Although  it  is  believed  that  the  corpuscles  are  constantly  being 


52  THE  EVOLUTION  OF  MAN 

destroyed,  little  is  known  as  to  where  or  how  the  destructive 
process  occurs.  Sometimes  they  seem  to  be  destroyed  much 
faster  than  they  are  formed  and  this  results  in  a  great  reduc- 
tion of  the  number  of  the  red  blood  cells  of  the  body  from 


Middle  lobe 

of  thyroid  gland. 

Thymus  gland. 
Lateral  lobe 

of  thyroid  gland. 

Trachea. 
Lung. 


Right  lobe  of  liver. 


Vitelline  duct. 


Pharyngeal 
pouches. 


Stomach. 


Pancreas. 

Left  lobe  of  liver. 


Small  intestine. 


Large  intestine. 


Fig.  19.  Organs  developing  from  the  rudi- 
mentary alimentary  canal.  After  Bonnet. 
From  Heisler,  Embryology.  By  permission 
of  W.  B.  Saunders  and  Co. 

5,000,000  to  perhaps  1,000,000  per  cubic  millimeter,  together 
with  the  appearance  also  of  a  certain  number  of  the  embry- 
onic type  of  nucleated  red  cells  in  the  blood  stream.  Evidently 
the  immature  cells  are  drawn  into  the  blood  stream  in  the 
endeavor  to  make  good  the  excessive  loss.  This  is  the  condi- 
tion which  exists  in  that  quite  fatal  disease,  pernicious  anaemia. 


THE  NATURAL  HISTORY  OF  MAN  53 

Reproductive  System.  The  gonads,  in  which  the  germinal 
cells  form,  are  developed  in  the  body  cavity  just  at  the  lower 
end  of  the  kidneys,  probably  from  mesodermal  cells,  and  early 
begin  to  move  downward  in  the  abdomen.  In  the  female  they 
go  as  far  as  the  pelvic  cavity  where  they  remain.  In  the  male 
they  pass  through  a  canal  in  the  lower  part  of  the  abdominal 
wall,  called  the  inguinal  canal,  to  the  exterior  of  the  body. 
Similar  migrations  of  the  gonads  occur  in  most  mammals.  The 
reasons  for  these  migrations  are  not  known,  but  the  inguinal 
canal  remains  as  a  weak  spot  in  the  abdominal  wall  and  under 
special  stress  may  permit  loops  of  the  intestines  to  pass 
through,  thus  forming  a  hernia.  This  is  the  penalty  man  is 
still  paying  for  the  lack  of  structural  adjustment  to  the  upright 
position. 

The  external  genital  organs  develop  in  a  similar  way  in 
both  sexes  and  no  structural  distinction  is  to  be  observed  until 
near  the  beginning  of  the  third  month  of  fetal  life.  At  this 
time  the  indifferent  sex  condition  begins  to  develop  into  one 
sex  or  the  other  by  the  greater  growth  of  some  parts  and  the 
partial  suppression  of  others,  depending  upon  the  sex  to  be 
formed.  In  rare  cases  the  indifferent  condition  of  the  sex 
organs  may  persist  permanently  in  either  sex,  a  condition 
known  as  spurious  hermaphroditism,  which  has  particular  in- 
terest to  criminologists  and  sociologists.  The  urinary  system 
develops  in  close  relationship  to  the  genital  system  and,  before 
the  permanent  adult  condition  is  reached,  passes  through  a 
remarkable  series  of  changes,  many  of  which  are  typical  of  the 
permanent  adult  condition  in  the  lower  vertebrates. 

The  Muscles.  As  noted  above,  the  mesoderm,  which  lies 
along  each  side  of  the  developing  spinal  cord,  becomes  trans- 
versely divided  into  a  linear  series  of  segments  (Fig.  14). 
This  process  begins  when  the  embryo  is  about  two  weeks  old 
and  continues  until  a  total  of  thirty-eight  segments  are  formed 
which  extend  the  entire  length  of  the  embryo.     From  these 


54  THE  EVOLUTION  OF  MAN 

segments  are  developed  all  the  muscles  of  the  body,  the  axial 
part  of  the  skeleton,  and  the  membranes  surrounding  the 
brain   and  spinal  cord.     Although  the  muscles   are   at  first 


Fig.  20.  Diagram  showing  the  development  of  the  human  heart  and  the 
changes  of  form  and  external  appearance  at  different  stages.  Modified  from 
His's  models.  Figs.  Ill  B  and  IV  B  are  side  views;  the  others  are  front  views. 
a,  primitive  ventral  aorta;  b,  bulbus  cordis;  c,  ventricle;  c',  left  ventricle;  d, 
auricle ;  d',  left  auricle ;  e,  sinus  venosus ;  f,  atrio-ventricular  canal ;  g,  position 
of  orifice  of  atrio-ventricular  canal ;  h,  vitelline  vein.  Redrawn  from  Cunning- 
ham, Anatomy, 


THE  NATURAL  HISTORY  OF  MAN  55 

separate  masses,  by  a  process  of  fusion  of  the  segments  and 
then  a  later  splitting,  either  lengthwise  or  tangentlally,  the 
long,  flat  muscles  In  the  front  and  back  of  the  body  are  formed. 
Also  many  muscles  shift  from  their  early  positions  to  some 
quite  distant  place.  This  Is  the  case,  for  example,  with  the 
muscular  diaphragm,  which  forms  in  the  neck  and  is  supplied 
by  a  nerve  from  this  region  but  which,  during  development, 
moves  posteriorly  dragging  its  nerve  with  It,  until  in  the  final 
position  it  separates  the  thorax  from  the  abdomen.  All  of 
this  differentiation  and  shifting  of  muscles  has  been  com- 
pleted some  time  before  the  child  is  born  and  therefore  is  not 
produced  by  any  functional  necessities  after  birth,  but  is  due 
to  heredity. 

The  Limbs.  Until  the  beginning  of  the  fourth  week  of  de- 
velopment, man  is  a  limbless  vertebrate  (Fig.  23).  The  rudi- 
ments of  the  limbs  then  grow  out  as  buds  from  the  side  of 
the  body  and,  as  they  elongate,  five  projections  appear  at  the 
end  of  each  of  the  buds  which  represent  the  developing  fingers 
and  toes.  This  peripheral  cleavage  into  five  parts  perhaps 
is  representative  of  the  five  main  segments  of  the  body  from 
which  the  limb  projects.  Inasmuch  as  the  five-fingered,  or 
pentadactyl,  limb  is  the  common  vertebrate  type  it  is  believed 
that  polydactylism,  or  an  extra  number  of  fingers  or  toes.  Is 
not  a  reversion  to  an  ancestral  form  but  is  due  to  an  unknown 
cause. 

The  Skeleton.  The  skeleton  is  preceded  In  very  early  pre- 
natal life  by  two  kinds  of  material,  cartilage  and  membrane. 
While  most  of  the  bones  of  the  skeleton  are  ossified  from  car- 
tilage, the  bones  of  the  cranium  are  largely  developed  from 
membrane.  The  cranial  bones  begin  ossification  at  their 
centers  near  the  end  of  the  second  month  of  prenatal  life,  the 
growth  of  the  cranium  being  due  chiefly  to  additions  at  the 
edges  of  the  bones.  In  the  long  bones,  like  the  femur  and 
humerus,  which  are  mapped  out  in  cartilage,  the  centers  of 


S6  THE  EVOLUTION  OF  MAN 

ossification  appear  about  the  eighth  week  of  prenatal  life  in 
the  center  of  the  shaft,  and,  at  birth,  while  the  shaft  is  bone, 
both  extremities  are  still  cartilaginous. 

The  Skin.  The  outside  portion  of  the  skin,  or  epidermis,  is 
derived  from  the  ectoderm,  while  the  deeper  portion,  or 
dermis,  is  developed  from  the  mesoderm.  The  human  skin 
at  the  end  of  the  second  prenatal  month  is  translucent  and  has 
many  points  in  common  with  that  of  fishes  and  amphibians. 
In  the  third  month  a  delicate,  superficial,  horny  stratum  ap- 
pears, a  stage  which  has  been  held  to  represent  the  evolution 
from  an  aquatic  to  a  terrestrial  form  of  life. 

Hairs  are  outgrowths  from  the  epidermis  and  are  developed 
in  groups  and  lines.  Their  arrangement  can  best  be  explained 
on  the  supposition  that  originally  the  skin  was  covered  by 
scales  and  that  the  hair  grew  out  in  groups  at  their  tessellated 
junctions  as  is  found  In  certain  of  the  edentates.  The  skin  of 
man,  in  comparison  with  that  of  the  other  primates.  Is  com- 
paratively hairless,  which  is  probably  a  recently  acquired 
character.  At  the  seventh  month  of  prenatal  life  the  chim- 
panzee and  gorilla  have  well-developed  hair  on  the  scalp,  eye- 
brows, and  lips,  while  the  rest  of  the  body  Is  covered  with  fine 
hair.  This  Is  also  the  condition  of  the  human  fetus  at  a  corre- 
sponding period.  The  hair  slopes  In  man  are  also  very  similar 
to  those  of  the  apes.  Some  hairs,  such  as  those  present  in  the 
eyebrows,  perhaps  originally  had  a  sensory  function  and.  In 
general,  hair  appears  to  be  a  modification  of  certain  glandu- 
lar and  sensory  structures  found  in  the  skin  of  the  amphibians. 
Evidence  has  accumulated  which  shows  that  the  development 
of  the  hair  is  regulated,  at  least  to  some  degree,  by  an  internal 
secretion  of  the  thyroid  and  sex  glands. 

Face  and  Nose.  The  face  is  developed  from  a  series  of 
paired  processes  surrounding  the  primitive  mouth  (Fig.  21). 
These  grow  In  from  the  sides  toward  the  mid-ventral  line 
where  they  normally  fuse  by  the  third  prenatal  month,  by  a 


Fig.  21.  The  development  of  the  face  of  a  human  embryo 
(His).  From  Prentiss  and  Arey,  Embryology.  By  permission 
of  W.  B.  Saunders  and  Co. 


THE  NATURAL  HISTORY  OF  MAN  57 

method  somewhat  akin  to  the  healing  of  wounds,  to  form  the 
nose  and  lips.  A  failure  of  proper  fusion  of  these  processes 
results  in  harelip  and  various  other  facial  deformities. 

In  the  development  of  the  human  nasal  cavity  a  recapitula- 
tion of  the  conditions  present  in  the  various  classes  of  verte- 
brates is  to  be  noted.  At  the  end  of  the  third  week  of  fetal 
life  the  rudiments  of  the  olfactory  organ  appear  as  two  thick- 
ened plates  of  ectoderm  which  are  in  contact  with  the  under 
surface  of  the  fore-brain.  A  week  later  these  plates  become 
depressed  and  are  found  at  the  bottom  of  the  olfactory  pits. 
This  condition  is  similar  to  that  found  in  fishes.  Two  weeks 
later  the  depression  has  deepened  and  a  nasal  cavity  is  formed 
which  is  somewhat  similar  in  structure  to  that  found  in  the 
air-breathing  or  lung  fishes.  By  the  seventh  week  this  primi- 
tive nasal  cavity  has  rapidly  enlarged  and  a  communication 
has  been  made  with  the  mouth  as  in  amphibians.  The  mam- 
malian condition  is  reached  by  the  third  month.  At  this  time 
the  roof  of  the  mouth  is  completed  by  the  growth  to  the  center 
and  fusion  of  two  lateral  shelves.  A  failure  of  these  shelves 
to  unite  produces  cleft  palate. 

The  teeth  are  formed  by  local  outgrowths  of  the  ectoderm 
and  mesoderm  lining  the  mouth,  the  enamel  being  formed 
from  the  ectoderm,  and  the  dentine  and  pulp  from  the  meso- 
derm. The  human  molars  with  their  several  cusps  have 
evolved  from  the  simple  conical  teeth  of  fishes  and  reptiles 
either  by  a  process  of  partial  fusion  or  by  an  outgrowth  of 
cusps  from  the  conical  tooth. 

The  Prenatal  Nourishment  of  the  Embryo.  During  pre- 
natal life  the  fetus  is  enclosed  in  a  fluid-filled  sac,  the  wall  of 
which  is  composed  of  two  membranes,  the  inner  called  the 
amnion  and  the  outer  the  chorion,  which  serve  for  protection 
and  nutrition  (Fig.  12).  The  development  of  an  embryo  in 
utero  is  dependent  upon  its  ability  to  secure  nourishment  and 
to  eliminate  certain  wastes.     In  order  to  do  this  it  must  get 


58  THE  EVOLUTION  OF  MAN 

into  contact  with  the  maternal  blood  supply  in  the  walls  of 
the  uterus.  It  appears  that,  in  this  early  stage,  the  outer  layer 
of  embryonic  cells  is  able  to  secrete  a  ferment,  or  enzyme, 
which  actually  eats  away,  or  digests,  a  portion  of  the  uterine 
wall  with  which  it  is  in  contact.  This  process  furnishes  the 
embryo  with  a  temporary  supply  of  food  which  can  be  ab- 
sorbed by  the  cells  and  also  enables  it  to  imbed  itself  com- 
pletely in  the  uterine  wall  where  it  is  surrounded  with  extra- 
vascular  blood,  the  result  of  the  erosion  of  maternal  blood 
vessels.  In  a  short  time  a  certain  region  of  the  outer  layer 
of  cells  together  with  the  underlying  chorion  becomes  modified 
to  form  a  highly  specialized  structure,  the  placenta,  through 
which  an  interchange  of  materials  between  the  mother  and 
embryo  can  take  place.  The  fetal  placental  tissues  become 
actually  fused  with  the  uterine  wall  (Fig.  22),  and  the  under- 
lying tissue  of  the  latter  is  gradually  eroded  to  such  an  extent 
that  the  finger-like  processes,  or  villi,  of  the  fetal  tissues  of 
the  placenta,  which  project  into  the  maternal  tissue,  are  sur- 
rounded by  intervillous  spaces  of  considerable  size  which  are 
filled  with  the  maternal  blood  (Fig.  22).  Although  the  pla- 
cental villi  are  richly  suppHed  with  fetal  blood  vessels  there  is 
never  any  direct  connection  between  the  maternal  and  fetal 
blood  vessels  in  the  placenta,  and  no  nerves  pass  from  the 
mother  to  the  child.  The  interchange  of  materials,  oxygen 
and  food  from  the  maternal  to  the  fetal  circulation,  and  carbon 
dioxide  and  hquid  metabolic  wastes  from  the  fetal  to  the 
maternal,  all  takes  place  by  osmosis  and  specific  selection. 
The  structure  of  the  placenta  in  the  different  mammals  shows 
considerable  variation.  That  found  in  the  anthropoid  apes 
is  very  similar  to  the  human  type. 

The  maternal  and  fetal  blood  streams  are  separated  by  the 
embryonic  tissue  of  the  placental  villi  (Fig.  22) .  This  separa- 
tion can  be  proved  by  the  microscopic  examination  of  the  con- 
tents of  the  fetal  vessels  in  the  placental  villi  and  the  maternal 


Fig.  22.  The  relation  of  the  fetal  to  maternal  blood  in  the  placenta. 
Arrows  indicate  the  supply  and  exhaust  of  the  maternal  blood  in  the 
large  intervillous  spaces,  a,  sinus  of  uterine  vein;  b,  muscle  tissue  of 
uterine  wall;  c,  uterine  vein;  d,  uterine  artery;  e,  sinus  of  uterine 
vein;  f,  decidua  basalis;  g,  uterine  artery;  h,  intervillous  space  filled 
with  maternal  blood;  i,  syncytium;  j,  villus;  k,  umbilical  vein  (fetal)  ; 
1,  umbilical  artery  (fetal)  ;  m,  uterine  artery.  From  Prentiss  and 
Arey,  Embryology.     By  permission  of  W.  B.  Saunders  and  Co. 


THE  NATURAL  HISTORY  OF  MAN  59 

blood  in  the  placental  sinuses  in  the  early  stages  of  develop- 
ment. Many  nucleated  red  corpuscles  which  are  found  only 
in  the  blood  of  the  fetus  will  be  seen  in  the  vessels  of  the 
placental  villi  but  there  are  none  in  the  placental  sinuses. 
Further,  the  vessels  in  the  placental  villi  can  be  injected  from 
the  fetal  but  not  from  the  maternal  blood  vessels. 

That  gases  can  be  transmitted  from  the  maternal  to  the 
fetal  circulation  is  shown  by  the  fact  that  the  blood  in  the  um- 
bilical vein,  which  carries  blood  from  the  placenta  to  the  fetus, 
is  redder  and  contains  more  oxygen  than  the  darker  blood  of 
the  umbilical  artery,  which  carries  blood  from  the  child  to  the 
placenta.  Also  ether  or  chloroform  administered  to  the 
mother  can  be  demonstrated  in  the  blood  of  the  child. 

Substances  in  solution  also  can  pass  from  the  maternal  to 
the  fetal  blood.  This  is  indicated  by  the  fact  that  the  child 
grows.  Also  it  has  been  experimentally  demonstrated  in  the 
case  of  many  drugs  that  when  they  are  administered  to  the 
mother  they  will  be  found  in  the  blood  of  the  child.  Among 
these  drugs  are  bromide  of  potassium,  arsenic,  strychnine, 
quinine,  and  morphine. 

The  work  of  recent  observers  seems  to  show  that  fats  and 
proteins  are  not  passed  unchanged  through  the  walls  of  the 
placental  villi  from  maternal  to  fetal  blood,  but  are  broken 
down  into  simpler  compounds  and  later  recombined,  thus  mak- 
ing the  process  of  absorption  in  the  placenta  somewhat  analo- 
gous to  that  occurring  in  the  intestine.  The  placental  tissue 
apparently  has  not  only  the  power  to  change  some  substances 
but  also  the  power  of  specific  absorption.  Proteolytic,  lipo- 
lytic, and  glycolytic  ferments  have  been  demonstrated  in  the 
placental  villi,  also  a  ferment  which  changes  certain  of  the 
amino  acids  into  ammonia. 

Observers  now  generally  agree  that,  while  the  placenta 
usually  acts  as  an  efficient  filter  against  bacteria,  occasionally 
bacteria  may  be  transmitted  from  mother  to  child  as  has  been 


6o  THE  EVOLUTION  OF  MAN 

known  to  occur  in  some  cases  of  typhoid  fever  and,  in  rare 
instances,  of  tuberculosis.  On  the  contrary,  it  has  been  demon- 
strated that  the  toxins  and  antitoxins  of  diphtheria,  tetanus, 
and  typhoid  fever  readily  pass  from  the  maternal  to  the  fetal 
blood  stream  in  the  placenta.  Furthermore,  biologists  agree 
that  there  is  no  foundation  for  the  more  or  less  general  belief 
that  maternal  impressions  are  responsible  for  malformations 
of  a  child.  It  can  be  understood,  however,  that  a  general  dis- 
turbance of  the  fundamental  metabolic  processes  in  the  mother 
may  result  in  similar  disturbances  in  the  fetus  and  thus  may 
interfere  with  the  normal  developmental  processes. 

Birth.  It  has  been  seen  that  the  human  embryo  is  a  para- 
site which  engrafts  itself  on  the  maternal  tissues  and  by  the 
remarkable  and  highly  specialized  organ,  the  placenta,  is 
supplied  with  nourishment  and  relieved  of  its  wastes.  This 
connection  is  normally  retained  for  a  period  of  approximately 
nine  months,  at  which  time  the  'host,'  for  reasons  largely  un- 
known, refuses  longer  to  support  the  'parasite.'  Rhythmic 
contractions  begin  in  the  walls  of  the  uterus.  These  increase 
in  strength  and  frequency  and  finally  result  in  the  birth  of  the 
child.  In  separating  the  placenta  and  tearing  the  large  ma- 
ternal vessels  of  the  uterus,  without  causing  an  excessive 
hemorrhage,  nature  performs  a  wonderful  surgical  operation. 
The  moment  the  child  breathes  and  the  lungs  expand,  the 
course  of  the  circulation  is  changed.  This  change  is  due  to 
the  expansion  of  the  lungs  and  the  consequent  large  flow  of 
blood  to  them.  As  the  result  of  this,  the  opening  between  the 
two  auricles  (foramen  ovale)  closes,  the  course  of  the  circula- 
tion in  the  heart  is  also  changed  and  the  blood,  which  was 
formerly  aerated  in  the  placenta,  is  now  aerated  in  the  lungs. 
Sometimes  this  interauricular  opening  fails  to  close  in  the 
proper  manner  and  this  permits  a  mixture  of  venous  with 
arterial  blood  which  causes  a  dark  color  in  the  skin  and,  there- 
fore, what  is  commonly  known  as  a  'blue  baby.' 


THE  NATURAL  HISTORY  OF  MAN  6i 

In  the  prenatal  condition  the  child  needs  to  produce  very 
little  heat  because  so  little  is  radiated  and  the  mother  supplies 
all  of  the  necessary  food  and  oxygen  and  removes  all  the 
wastes.  After  birth  the  radiation  of  heat  is  greater  and  the 
child  is  obliged  to  produce  much  more  in  order  to  maintain  its 
body  temperature.  The  alimentary  canal  must  take  in  and 
digest  its  own  food;  through  its  lungs  the  child  must  obtain 
oxygen  and  free  itself  of  carbon  dioxide,  and  its  excretory 
organs  must  remove  its  own  wastes.  It  is  evident,  from  the 
above,  that  there  is  a  great  contrast  between  the  prenatal 
and  postnatal  environment,  and  the  fundamental  changes  in 
circulation,  nutrition,  and  excretion  which  occur  at  the  time  of 
birth  make  this  period  a  very  critical  one  for  the  child. 

At  birth  the  child  weighs  about  seven  pounds,  and  is  twenty 
inches  in  height.  Its  upper  extremities  are  relatively  long,  and 
the  lower  extremities  short.  The  legs  are  partly  flexed,  the 
great  toe  abducted  and  the  soles  of  the  feet  turned  in.  The 
latter  is  believed  to  be  indicative  of  a  persistence  of  the  climb- 
ing position  which  existed  in  arboreal  man.  Additional  evi- 
dence along  this  line  is  to  be  found  also  in  the  remarkable 
power  of  the  hand  grip  of  the  child  during  the  first  month  of 
its  life.  At  this  time  the  infant  is  able  to  hold  its  weight  sus- 
pended by  its  hands,  a  power  which  is  later  lost.  When  the 
body  proportions  of  the  newly  born  child  are  compared  with 
those  of  the  adult  it  is  found  that  the  child  is  four  times  its 
head  height  while  the  adult  is  eight  times ;  that  the  upper  and 
lower  extremities  of  the  infant  are  equal  In  length  while  in  the 
adult  the  lower  extremities  are  longer  than  the  upper.  The 
long  arms,  short  legs,  flat  nose,  inverted  feet,  and  lack  of 
cervical  and  lumbar  curves  in  the  spinal  column  of  a  newly 
born  infant  constitute  a  remarkable  series  of  structural  re- 
semblances to  the  ape  which  later  disappear  as  the  adult  condi- 
tion is  reached.  The  child  at  birth  can  feel,  see,  taste,  and 
suffer  pain  but  It  is  deaf  for  about  twenty-four  hours.     Its 


62  THE  EVOLUTION  OF  MAN 

most  striking  characteristics,  In  contrast  to  the  lower  animals, 
are  its  helplessness  and  educabllity.  Its  helplessness  has  un- 
doubtedly been  an  important  factor  in  the  development  of  the 
family,  while  the  long  period  of  growth  before  maturity  is 
reached  has  exerted  a  great  influence  in  the  development  of 
man's  psychic  powers,  which  distinguish  him  so  markedly  from 
all  other  animals. 

Statistics  of  various  animals  show  that  the  proportion  of 
male  and  female  births  is  approximately  equal;  the  ratio  in 
man  being  about  io6  males  to  lOO  females.  Multiple  births 
are  the  usual  rule  in  most  of  the  lower  mammals  but  not  in  the 
primates.  Occasionally,  however,  it  occurs  and  in  man  even 
sextuplets  have  been  recorded.  There  have  been  some  500 
theories  proposed  as  to  the  cause  of  sex  determination  and 
as  to  methods  for  controlling  it,  but  the  accumulated  evidence 
of  the  last  few  years  clearly  shows  that  sex  is  determined  at 
the  time  of  fertilization,  just  as  are  all  somatic  characters, 
and  that  it  cannot  later  be  changed  by  any  means.  Inasmuch 
as  the  ossification  of  the  bones  of  a  female  embryo  precedes 
slightly  that  of  the  male  embryo,  a  radiograph  may  perhaps 
aid  in  ascertaining  the  sex  of  the  child  before  birth. 

If  we  summarize  the  facts  regarding  man's  early  develop- 
ment, which  are  given  above,  it  is  evident  that  he  starts  his 
development  as  a  unicellular  animal,  becomes  a  metazoan  of 
the  Invertebrate  type,  develops  the  structure  of  a  vertebrate, 
and  ultimately  becomes  a  mammal.  Many  of  the  structures 
of  his  body  pass  through  temporary  stages  which  are  typical  of 
the  adult  condition  in  various  classes  of  the  vertebrates  and, 
in  general,  his  organs  are  developed  in  a  manner  similar  to 
that  in  other  animals.  Man's  development,  however,  parallels 
that  of  the  anthropoid  apes  for  a  longer  time  than  that  of 
other  mammals  and  at  birth  the  child  has  ape-like  characters 
that  later  disappear.  These  facts  of  human  development 
associate  man  closely  with  the  anthropoid  apes  and  give  evi- 


PIG 


RABBIT 


MONKEY 


MAN 


Fig.  23.  Comparison  of  the  embryos  of  the  Pig,  Rabbit,  Monkey,  and  Man 
at  corresponding  stages  of  development.  The  embryos  of  each  animal  are 
arranged  in  the  vertical  columns  according  to  age,  beginning  with  the  youngest 
stage  at  the  top.  Stage  A  of  the  human  embryo  is  fully  labelled  and  the  cor- 
responding structures  in  the  other  embryos  can  be  noted,  a,  head  region;  b, 
eye;  c,  ear;  d,  gill  slits;  e,  heart;  f,  fore  limb;  g,  primitive  muscle  segments; 
h,  hind  limb;  i,  tail  region.    Slightly  modified  from  K.  Guenther,  after  Keibel. 


THE  NATURAL  HISTORY  OF  MAN  63 

dence  that  the  latter  reproduce,  in  many  respects,  a  compara- 
tively recent  phase  in  the  history  of  human  evolution. 

Postnatal  Development 

In  the  final  analysis,  growth  in  any  living  organism  is  the 
result  of  the  division  of  a  cell  into  two  daughter  cells  each  of 
which,  when  first  formed,  is  half  the  size  of  the  original  cell. 
The  daughter  cells  very  soon,  by  the  process  of  intussuscep- 
tion which  undoubtedly  involves  complex  physico-chemical 
processes,  grow  to  the  size  of  the  original  cell  and  then  the 
process  can  be  repeated.  In  prenatal  life,  the  embryonic  cells, 
in  general,  divide  comparatively  rapidly  and,  as  a  rule,  are  not 
as  large  as  in  postnatal  development.  The  increase  in  size 
after  birth  is  believed  to  be  due  primarily  to  a  general  increase 
in  the  size  of  the  cells  of  the  body  rather  than  to  the  formation, 
by  cell  division,  of  additional  cells.  Development  is  therefore 
accomplished  by  cell  division,  cell  enlargement,  and  cell  differ- 
entiation. 

The  ultimate  size  of  an  animal  depends  both  upon  the  rate 
and  the  duration  of  growth.  Minot  has  shown  that  man 
becomes  larger  than  the  rabbit,  not  because  of  a  more  rapid 
growth,  but  because  he  grows  for  a  longer  period  of  time. 
The  rabbit,  on  the  other  hand,  becomes  larger  than  the  guinea 
pig  because  of  a  more  rapid  rate  of  growth.  Large  animals, 
with  few  exceptions,  continue  to  grow  during  a  longer  period 
and  live  longer  than  do  small  animals.  Statistical  studies  show 
that  the  rate  of  growth  is  most  rapid  in  early  prenatal  life  and 
steadily  diminishes  until  birth.  During  the  prenatal  period 
of  the  human  embryo  the  weight  increases  more  than  5,000,- 
000  times,  while  after  birth  the  increase  is  only  20.6 
times.  As  the  rate  of  growth  is  a  constantly  decreasing 
one,  its  cessation  seems  to  be  the  final  term  of  a  diminishing 
series.  During  the  most  rapid  period  of  growth  the  cells  have 
large  nuclei  but,  with  advancing  age,  the  cytoplasm  relatively 


64  THE  EVOLUTION  OF  MAN 

increases  and  this  change  in  the  relative  size  of  nucleus  and 
cytoplasm  constitutes  the  chief  structural  difference  between 
the  cells  of  the  young  and  of  the  old.  A  decreasing  rate  of 
growth  is  also  accompanied  by  a  diminution  in  the  water 
content  of  the  body,  as  is  shown  by  the  fact  that  in  the  first 
month  of  prenatal  life  the  percentage  of  water  in  the  body 
is  97.5  per  cent,  at  birth  it  has  become  74.7  per  cent,  and  at 
maturity  58.5  per  cent. 

While  man  and  the  higher  vertebrates  have  a  definite  period 
of  growth  some  fishes  and  amphibians  continue  to  grow 
throughout  life.  The  forces  which  stimulate  or  inhibit  growth 
are  largely  unknown.  Evidence  is  accumulating  to  show  that 
certain  of  the  internal  secretions,  notably  those  given  off  by 
the  thyroid  and  pituitary  glands,  play  a  large  part  in  the  con- 
trol of  growth.  It  is  believed  that  too  much  secretion  of  the 
latter  may  increase  the  growth  of  local  areas  of  the  body  such 
as  the  hands  and  face.  This  condition  is  to  be  seen  in  the  rare 
disease  known  as  acromegaly.  On  the  other  hand,  a  dimin- 
ished secretion  of  the  thyroid  results  in  a  failure  of  growth  of 
the  entire  body  as  well  as  a  lack  of  mental  development,  a 
condition  known  as  cretinism.  Various  factors  such  as  un- 
favorable climatic  conditions,  poor  food,  lack  of  proper  pro- 
teins and  vitamines,  and  severe  illness  retard  growth. 

However,  these  factors  do  not  offer  any  explanation  as  to 
why  most  animals  stop  growing  after  reaching  the  size  of  the 
species.  A  mouse  never  grows  to  the  size  of  an  elephant,  nor 
does  an  elephant  remain  as  small  as  a  mouse.  It  is  apparent 
that  there  is  a  fundamental  hereditary  factor  involved  which  in 
some  way,  possibly  through  the  internal  secretions,  controls 
growth.  That  this  hereditary  influence  has  not  always  re- 
mained constant  is  shown  in  the  size  variation  of  the  same 
species  in  different  geologic  ages.  This  is  notably  shown  in 
the  evolution  of  the  horse.  The  question  of  growth  is  closely 
associated  with  the  power  of  regeneration,  that  is,  the  abilii 


THE  NATURAL  HISTORY  OF  MAN  6$ 

of  an  animal  to  replace  lost  parts.  The  power  of  regeneration 
In  an  animal,  In  general,  Is  found  to  be  In  Inverse  ratio  to  the 
degree  of  specialization,  or  differentiation,  which  it  exhibits. 
For  example,  among  the  lower  vertebrates,  the  amphibia  are 
able  to  regenerate  entire  limbs,  whereas  In  the  more  highly 
specialized  animals  such  as  man  this  power  of  regeneration 
is  present  only  in  certain  tissues,  notably  the  connective  and 
epithelial,  by  the  agency  of  which  wounds  are  healed.  Cancer 
is  generally  regarded  as  a  localized  lawless  and  unrestrained 
growth  of  epithelium,  the  cells  having  become  parasites  and 
attacked  the  host.  The  only  cure  thus  far  discovered  is  an 
early  destruction  or  removal  of  the  abnormal  parasitic  cells. 
The  causation  of  cancer  apparently  lies  In  the  disturbed  bal- 
ance of  the  forces  stimulating  and  restraining  growth  in  the 
affected  cells  and  is  probably  essentially  a  faulty  cellular 
chemistry. 

The  child  sits  up  by  the  sixth  month,  creeps  by  the  tenth 
month,  and  walks  by  the  fifteenth  month,  thus  passing  from  a 
quadrupedal  gait  to  the  erect  position  in  a  few  months,  an 
accomplishment  which  in  evolution  may  have  occupied  ages. 
All  parts  of  the  child  do  not  grow  at  the  same  rate  and,  as 
a  result,  the  body  proportions  continually  change  during 
growth  (Fig.  24).  Even  the  shaping  of  the  features  is  due  to 
the  different  rates  of  growth  of  the  various  parts  of  the  face. 
Comparing  the  condition  at  birth  with  that  of  maturity  it  is 
found  that  while  the  head  doubles  in  height,  the  body  increases 
three  times,  the  upper  limbs  four  times,  and  the  lower  limbs 
five  times.  These  changes  In  the  body  proportions  are  well 
shown  If,  with  the  adult  proportions,  we  compare  the  pro- 
portions of  the  child  when  expanded  to  the  height  of  the  adult. 
Such  a  comparison  will  show,  as  has  been  previously  noted, 
that  the  head  of  the  adult  Is  relatively  smaller,  the  arms 
shorter,  and  the  legs  longer  (Fig.  24) . 

Likewise  It  Is  known  that  various  organs  grow  at  different 


66  THE  EVOLUTION  OF  MAN 

rates  with  the  result  that  they  bear  a  different  ratio  to  the  total 
body  weight  at  different  ages.  Here  is  a  field  that  needs  much 
further  study  inasmuch  as  this  changing  relationship  in  size 
may  have  an  important  bearing  on  the  incidence  of  disease  at 
different  ages.     The  studies  which  have  been  made  on  the 


2  mo.  (fetal) 


5  mo. 


Newborn 


2yrs. 


6  yrs. 


12  yrs. 


25  yrs. 


Fig.  24.  Changes  in  proportion  during  prenatal  and  postnatal  growth. 
After  Stratz.  From  Morris's  Human  Anatomy.  By  permission  of  P.  Blakis- 
ton's  Son  &  Co. 


relative  growth  of  the  different  organs  show  that  the  same 
proportionate  weight  of  the  skeleton,  fat,  and  skin,  which  is 
about  39  per  cent  of  the  total  weight  of  the  new-born,  persists 
in  the  adult;  that  the  relative  weight  of  the  organs  of  circula- 
tion, respiration,  and  alimentation  is  about  twice  as  large  in  the 
new-born  as  in  the  adult;  that  the  weight  of  the  muscles  of  the 
new-born  is  relatively  one  half  as  large  as  in  the  adult,  and, 
that  the  central  nervous  system  of  the  new-born  is  relatively 
eight  times  as  large  as  in  the  adult.  It  is  possible  that  the  very 
rapid  growth  of  the  brain  in  early  childhood  accounts  in  part, 
at  least,  for  the  nervous  instability  of  that  period. 

Considerable   data   have   accumulated  with  regard  to  the 
growth  of  bone.     Membrane  bones,  such  as  the  bones  of  the 


THE  NATURAL  HISTORY  OF  MAN  67 

cranium,  grow  by  additions  along  their  edges  which  form  the 
sutures.  Beginning  at  about  forty  years  of  age,  when  the  brain 
stops  growing,  the  cranial  sutures  disappear.  In  the  long  limb 
bones  in  early  postnatal  life,  one  or  more  centers  of  ossifica- 
tion appear  in  the  terminal  cartilages  and  form  caps  of  bone. 
The  growth  in  length  occurs  in  the  cartilage  under  the  bony 
caps.  This  was  shown  experimentally  many  years  ago  by 
John  Hunter,  who  inserted  shot  in  the  shaft  and  in  the  end 
cap  of  a  femur  in  a  young  animal,  and  later  found  that  the  dis- 
tance between  them  had  increased.  Usually  by  the  twenty-first 
year  these  caps  have  joined  to  the  shaft  thus  making  any 
further  growth  In  length  impossible.  The  growth  in  the  cir- 
cumference of  a  bone  takes  place  by  additions  under  the  outer 
fibrous  membrane,  known  as  the  periosteum.  This  has  been 
shown  experimentally  by  feeding  growing  animals  with  madder, 
which  gives  a  yellowish  stain  to  the  new  bone. 

The  child,  like  the  young  of  all  mammals,  is  born  without 
teeth.  The  first  set,  twenty  in  number,  begins  to  erupt  about 
the  sixth  month  after  birth  and  is  completed  when  the  child  is 
nearly  two  and  one  half  years  of  age.  During  the  next  few 
years  the  permanent  teeth,  thirty-two  in  number,  are  forming 
beneath  the  temporary  teeth  and  also  behind  them,  and,  by  the 
absorption  of  their  roots,  replace  them.  The  first  permanent 
tooth  to  erupt  is  the  first  molar  which  appears  behind  all  the 
temporary  teeth  at  the  sixth  year.  By  thirteen  years  of  age 
all  of  the  permanent  teeth  have  erupted  except  the  third 
molars,  or  wisdom  teeth,  which  appear  about  the  seventeenth 
year.  The  latter  may  be  small  in  size,  be  abnormally  placed, 
appear  late,  or  even  fail  entirely  to  appear. 

A  study  of  the  growth  curves  for  height  and  weight  (Fig. 
25),  which  have  been  plotted  by  averaging  the  results  obtained 
from  weighing  and  measuring  many  children  at  various  ages, 
but  mostly  over  five  years  of  age,  shows  a  general  agreement 
of  results.     There  is  a  loss  of  weight  for  the  first  few  days 


68  THE  EVOLUTION  OF  MAN 

after  birth,  the  postnatal  retardation.     During  the  first  year, 

growth  in  both  weight  and  height  is  rapid — the  boy  increasing 


YEARS 
eO  25 


140 


Fig.  25.     Growth  curves  for  increase  in  weight  and  stature 
for  both  sexes.     From  Donaldson,  after  Roberts. 


THE  NATURAL  HISTORY  OF  MAN  69 

more  rapidly  than  the  girl — then  the  rate  of  growth  goes  on 
more  slowly  up  to  seven  years  of  age.  This  is  followed  by  a 
more  rapid  Increase  In  growth  rate  up  to  about  seventeen  years 
in  the  boy  and  sixteen  years  In  the  girl,  with  a  prepubertal 
acceleration  present  in  both  sexes.  The  growth  rate  then  de- 
creases to  twenty-five  years  of  age,  at  which  time  growth  prac- 
tically ceases. 

During  the  early  years  the  boy  is  slightly  taller  and  heavier 
than  the  girl  but,  owing  to  an  earlier  prepubertal  acceleration 
in  the  girl,  the  two  sexes  are  equal  in  height  at  twelve  years  of 
age  and  for  the  next  three  years  the  girl  Is  the  taller.  Simi- 
larly, at  thirteen  years  of  age,  the  two  sexes  are  of  equal  weight 
and  for  the  next  three  years,  the  girl  Is  the  heavier.  After 
fifteen  years  of  age  the  boy  surpasses  the  girl  In  height  and 
after  sixteen  years  In  weight.  The  average  height  for  the 
people  In  the  United  States  Is  about  five  feet  and  eight  Inches 
for  men,  and  ^vq  feet  and  four  inches  for  women.  On  the 
other  hand  some  of  the  dwarf  races  of  central  Africa  scarcely 
attain  four  and  one  half  feet  In  height.  The  average  weight 
of  the  male  Is  150  pounds  and  of  the  female  125  pounds. 

Puberty.  At  puberty  certain  marked  physical  and  psychic 
characters,  known  as  the  secondary  sexual  characters,  develop 
which  quite  clearly  distinguish  the  sexes.  These  changes,  as 
experimental  work  on  the  lower  animals  has  shown,  are 
brought  about  by  the  Internal  secretions  of  the  sex  glands  and 
can  be  prevented  by  their  early  removal.  Also  some  of  the 
sexual  characters  In  the  human  female  may  be  modified  to 
somewhat  resemble  the  male  after  the  climacteric  when  the 
internal  secretions  of  the  sex  glands  diminish  or  cease.  In  the 
male  the  growth  in  weight  and  height  Is  usually  greater,  the 
brain  and  face  grow  larger,  the  vocal  cords  elongate  rapidly, 
which  causes  the  pitch  of  the  voice  to  drop  an  octave,  the  beard 
develops,  the  muscles  become  larger,  giving  a  more  angular 
appearance  to  the  surface  of  the  body  in  marked  contrast  to 


70  THE  EVOLUTION  OF  MAN 

the  curves  of  the  female,  the  waist  is  broader,  the  pelvis 
smaller,  the  shoulders  less  sloping,  and  the  hands  and  feet 
larger. 

Senescence 

The  normal  life  cycle  has  three  phases,  development,  ma- 
turity, and  decline.  Each  of  the  first  two  phases  lasts  about 
thirty  years  and  the  third  should  be  at  least  of  equal  length. 
But  this  may  be  greatly  exceeded  as  shown,  for  example,  by 
the  longest  life  yet  recorded  in  modern  times;  that  of  Thomas 
Parr  of  England  who  was  one  hundred  fifty-two  years  and  nine 
months  old  when  he  died.  Old  age  in  itself  is  a  physiological 
condition  which  results  from  a  state  of  lessened  vitality  and 
activity  of  the  various  organs.  The  essential  factor  in  grow- 
ing old  is  a  progressive  degeneration  of  the  tissues,  as  a  result 
of  changes  in  the  cells  which  compose  them,  thereby  bringing 
about  a  gradually  diminishing  functional  capacity  of  the 
various  organs  until,  finally,  the  activity  of  some  vital  organ  or 
organs  ceases  and  physiological  death  results.  Certain  visible 
external  structural  changes  in  the  body  are  increasingly  in 
evidence  as  old  age  comes  on,  all  of  which  are  due  funda- 
mentally to  degenerative  changes  in  the  individual  cells  of  the 
various  tissues.  The  hair  turns  gray,  the  skin  loses  its  elas- 
ticity and  becomes  wrinkled.  Extensive  changes  occur  in  the 
jaws  which  are  due  to  a  loss  of  the  teeth,  with  a  consequent 
absorption  of  that  part  of  the  jaw  which  held  them,  resulting 
in  a  return  to  the  infantile  type  of  jaw.  The  walls  of  the 
arteries  harden  (arteriosclerosis)  and  the  blood  pressure  in- 
creases. There  is  a  progressive  loss  of  strength  and  elasticity 
in  the  muscles.  Some  of  the  cartilages  may  calcify,  the  bones 
become  more  fragile,  the  cranial  sutures  disappear,  and  there 
Is  a  decrease  in  the  stature.  The  near  point  of  vision  recedes, 
due  to  a  loss  in  elasticity  of  the  mechanism  of  accommodation. 
Changes  also  take  place  in  the  nervous  system.     These  are 


THE  NATURAL  HISTORY  OF  MAN  71 

associated  with  a  shrinkage  of  the  brain,  due  essentially  to  the 
atrophy  of  nerve  cells  in  the  cerebral  cortex,  and  bring  about 
a  loss  in  muscular  coordination  and  in  memory,  and  a  lack  of 
acuteness  in  the  senses.  Normally,  physical  decadence  occurs 
earlier  than  mental. 

It  is  very  difficult  to  distinguish  between  normal  senile  de- 
generative changes  and  those  due  to  disease.  For  example,  it 
seems  impossible  at  present  to  tell  whether  the  hardening  of 
the  arteries  is  to  be  considered  normal  or  abnormal  in  old  age. 
Also  we  know  very  little  of  the  chemical  alterations  in  the 
body  which  are  associated  with  advancing  age,  except  that  a 
relative  increase  in  the  salt  content  has  been  found.  In  fact, 
the  whole  subject  of  senescence  needs  renewed  investigation 
to  determine  what  constitutes  normal  senile  changes.  The 
striking  experiments  of  Steinach  and  others  have  shown,  in 
the  case  of  both  the  lower  animals  and  man,  that  at  least  a 
temporary  rejuvenescence  can  be  produced  in  the  old  by  en- 
grafting the  gonads  or,  in  the  male,  by  ligating  the  vas 
deferens. 

There  are  three  principal  theories  with  regard  to  the  bio- 
logical significance  of  old  age  and  natural  death.  The  first 
theory  is  that  old  age  is  a  pathological  condition  due  to  lack 
of  internal  adjustment  to  external  environment.  Metchnikoff 
was  an  advocate  of  this  and  held  that  there  is  a  constant  con- 
flict between  certain  cells  of  the  body,  some  trying  to  destroy 
the  others  which  are  essential  to  life.  This  they  may  accom- 
plish if  the  cells  acquire  a  lessened  resistance  as  a  result  of 
the  absorption  of  toxins  released  by  certain  bacteria  in  the 
intestines.  Hence  another  species  of  bacteria.  Bacillus  hul- 
garicus,  by  interfering  with  the  growth  of  the  toxin-producing 
bacteria,  becomes,  according  to  Metchnikoff,  a  "fountain  of 
youth."  According  to  the  second  theory,  which  was  advocated 
by  Weismann,  the  higher  organisms  have  acquired  senility  and 
natural  death  through  natural  selection  as  a  character  which 


72  THE  EVOLUTION  OF  MAN 

is  of  advantage  to  the  existence  of  the  species.  The  third 
theory,  which  was  advocated  by  Maupas  and  Minot,  holds 
that,  at  fertilization,  a  stimulus  is  supplied  to  the  developing 
organism  which  is  gradually  dissipated,  during  the  later  growth 
and  differentiation,  until  finally  none  is  left  and  the  organism 
dies  of  old  age.  As  the  phenomenon  of  old  age  is  a  common 
one  to  all  metazoan  animals  it  would  seem  that  the  third 
theory  is  more  in  accord  with  the  facts. 

Biologists  have  estimated  that  an  animal  should  live  from 
five  to  seven  times  the  period  of  growth.  This  means  that 
man  should  live  to  be  from  one  hundred  to  one  hundred  and 
forty  years  old.  The  facts  in  regard  to  different  animals,  how- 
ever, do  not  seem  to  support  this  view.  Rubner  has  estimated 
that  man  requires  about  four  times  as  many  food  calories  for 
the  period  from  the  cessation  of  growth  till  the  end  of  life  as 
other  mammals  and  he  interprets  this  as  meaning  that  the  hu- 
man cells  have  a  much  greater  total  capacity  for  obtaining 
energy  from  foodstuffs  than  those  of  other  mammals.  The 
cells  seem  to  be  able  to  make  only  a  limited  number  of  chemical 
transformations,  after  which  physiological  death  ensues.  Rub- 
ner believes  that  the  cells  in  man  can  make  a  greater  number 
of  such  transformations  than  those  of  most  other  mammals. 

Vestigial  Structures 

The  normal  life  cycle  of  man  having  now  been  considered, 
attention  should  be  given  to  another  valuable  line  of  evidence 
as  to  man's  origin,  namely,  certain  structural  features  known 
as  the  vestigial  organs  which,  although  practically  functionless 
in  man  at  the  present  time,  are  believed  to  be  the  remains  of 
well-developed,  functional  organs  in  the  past.  A  few  typical 
examples  may  be  noted. 

At  the  inner  corner  of  the  eye  is  a  fold  of  the  conjunctiva, 
the  mucous  membrane  covering  the  front  of  the  eyeball,  called 


THE  NATURAL  HISTORY  OF  MAN  73 

the  plica  semilunaris,  which  is  relatively  larger  during  prenatal 
life.  It  is  believed  to  be  a  reduced  third  eyelid,  such  as  is 
regularly  found  in  amphibia  and  birds,  by  which  the  eye  is 
closed. 

Man  possesses  muscles  which  are  arranged  to  move  the  ear 
either  as  a  whole  or  in  part,  but  he  has  entirely  lost  the  con- 
trol of  them  or  only  exceptionally  retains  partial  control. 
Probably  when  man  assumed  the  erect  posture  with  eyes  look- 
ing forward  the  head  became  more  movable  and  rendered 
unnecessary  the  mobility  of  the  ear  with  the  resulting  loss  of 
function  In  its  muscles.  At  one  period  during  prenatal  de- 
velopment the  human  ear  is  pointed  and  resembles  the  ear  of 
certain  monkeys.  This  point  persists  in  many  people  as  a 
projection  on  the  rolled  or  unrolled  rim  (helix)  of  the  ear. 
It  is  known  as  Darwin's  tubercle  and  is  the  vestigial  remains  of 
man's  ancestral  ear  point. 

Near  the  junction  of  the  large  and  small  intestine  in  man 
(Fig.  26)  there  is  a  narrow,  blind  process,  about  three  and  a 
half  inches  in  length,  known  as  the  vermiform  appendix.  The 
appendix  in  man  is  a  vestigial  structure  and  represents  the  func- 
tionless,  shriveled,  terminal  remains  of  the  caecum,  the  blind 
beginning  of  the  large  intestine.  In  an  herbivorous  animal, 
the  caecum  is  a  large,  nutritive  organ  of  great  Importance.  In 
carnivorous  animals,  the  caecum  is  reduced.  The  reduction  of 
the  terminal  portion  of  the  caecum  to  form  an  appendix  occurs 
only  in  man  (Fig.  26),  the  anthropoid  apes,  and  some  rodents. 
The  frequent  pathological  condition  of  the  appendix  in  man 
has  given  rise  to  the  aphorism  "that  vestigial  structures  are 
particularly  prone  to  disease." 

There  are  various  structures  in  the  body  which,  although 
not  vestigial,  give  evidence  of  a  retrogression.  Such  a  condi- 
tion Is  to  be  noted  in  certain  of  the  sense  organs.  The  olfac- 
tory organ,  for  example,  which  is  of  the  greatest  importance 
to  the  lower  mammals  and  other  classes  of  the  vertebrates. 


74  THE  EVOLUTION  OF  MAN 

has  become  very  much  reduced  in  man  and  is  represented  only 
by  a  small  part  of  the  nasal  mucous  membrane.     In  corre- 
spondence with  this  the  olfactory  portion  of  the  brain  is  also 
very  much  reduced. 
"•^Other  structures   showing  signs  of  retrogression  are  the 


faecum... 


A/ojoe-f^cZ/x. 


.Caecctm 


Fig.  26.  The  caecum  and  vermiform  appendix  in  various 
mammals.  1,  Horse;  2,  Kangaroo;  3,  Cat;  4,  Lemur;  5, 
Orang;  6,  Man,  fetal;  7,  Man,  adult.  Redrawn  from  Stratz, 
Naturgescliichte  des  Menschen.  By  permission  of  Ferdinand 
Ecke. 

teeth.  This  is  indicated  by  the  tendency  for  the  teeth  and 
jaws  to  become  ^mailer  and  is  very  evident  when  these  struc- 
tures in  civilized  man  are  compared  with  those  of  the  primitive 
races  and  with  fossil  man.  Additional  evidence  is  to  be  noted 
in  the  occurrence  of  misplaced  and  irregular  teeth  which,  in 


J 


THE  NATURAL  HISTORY  OF  MAN  75 

general,  signify  that  the  jaw  is  too  small.  Likewise  the  fact 
that  the  third  molars  and  lateral  incisors  are  variable  in  de- 
velopment and  frequently  fail  to  appear  indicates  a  tendency 
to  a  reduction  in  the  number  of  the  teeth.  A  comparison  of 
man's  dentition  with  that  of  a  typical  mammal  having  forty- 
four  teeth,  shows  that  man  has  probably  already  lost  twelve 
teeth  during  his  long  period  of  evolution.  The  projecting  chin 
which  man  alone  of  all  animals  possesses  is  the  result  of  the 
shrinkage  of  the  tooth-containing  part  of  the  jaw.  This  can 
be  well  illustrated  by  a  comparison  of  the  fossil  jaw  of  the 
Heidelberg  or  Neandertal  man  with  that  of  modern  man. 
iTooth  decay  also  is  not  found  so  extensively  in  the  primitive 
'races  as  in  the  civilized  and  is  apparently  absent  in  the  fossil 
races,  with  the  notable  exception  of  the  Rhodesia  man  recently 
found  in  the  Broken  Hill  mine.  It  is  clear  that  the  usual 
prophylaxis  against  tooth  decay  is  merely  temporizing  with 
the  real  problem.  Since  the  present  civilization  apparently 
carries  a  distinct  threat  to  the  teeth,  a  radical  change  in  diet 
and  habits  is  necessary  to  preserve  them.  What  such  change 
should  be  we  are  awaiting  our  nutrition  experts  to  show  us. 

Anatomical  Variations 

Finally,  further  evidence  as  to  the  ancestral  history  of  man 
can  be  obtained  from  a  study  of  structural  variations.  No 
two  people  are  exactly  alike  in  bones,  muscles,  or  vessels,  and 
even  the  nerves,  the  least  variable  structures  in  the  body,  show 
differences.  Some  of  these  variations  are  probably  fortuitous, 
others  are  to  be  considered  as  a  reversion  to  an  ancestral  form, 
and  still  others  progressive. 

Ordinarily  man  has  twelve  pairs  of  ribs  but  occasionally  a 
thirteenth  rib  appears.  This  is  known  as  a  cervical  rib  and  is 
located  in  the  neck  just  above  the  thorax.  It  is  generally 
reduced  in  length  but  may  be  long  enough  to  reach  the  sternum. 


76  THE  EVOLUTION  OF  MAN 

It  may  be  that  at  some  time  in  man's  ancestral  history  this  rib 
regularly  existed  but  now  it  occurs  only  occasionally  as  a  re- 
version to  an  ancestral  type.  Its  disappearance  may  perhaps 
be  associated  with  the  assumption  of  the  upright  gait,  with  the 
resulting  dragging  down  of  the  viscera  by  gravity.  A  tendency 
to  the  loss  of  more  ribs  is  seen  occasionally  in  the  partial 
deficiency  of  the  first  rib  and  in  the  absence  of  the  twelfth. 

Rarely  a  fourth  molar  tooth  occurs  in  man,  who  regularly 
has  only  three.  Some  of  the  lower  mammals  have  four  such 
teeth.  It  is  possible  that  the  fourth  molar  in  man,  when  it  ap- 
pears, is  a  reversion  to  the  former  condition.  This  tooth  is 
more  likely  to  occur  in  the  primitive  races  and  presumably 
occurred  still  more  frequently  in  those  prehistoric  races  which 
are  known  only  by  their  fossil  bones. 

In  about  four  per  cent  of  persons  a  small  muscle  exists  in  the 
front  of  the  thorax,  parallel  with  the  sternum,  known  as  the 
sternalis.  Anatomists  have  been  much  puzzled  for  an  explana- 
tion of  the  occasional  presence  of  this  muscle.  One  theory  is 
that  it  is  part  of  the  pectoral  muscle  which  in  some  unknown 
way  has  become  twisted  through  ninety  degrees.  That  this 
may  sometimes  be  the  proper  explanation  is  indicated  by  its 
receiving  a  branch  of  the  same  nerve  which  supplies  the  pec- 
toral muscle.  A  second  theory  is  that  the  sternalis  is  a  recur- 
rence of  part  of  the  subtegumentary  muscle  which  moves  the 
skin,  and  which  is  still  present  in  many  mammals  but  has  been 
largely  lost  in  man.  A  third  explanation  is  as  follows :  in  the 
amphibians  a  longitudinal  muscle  runs  from  the  pelvis  along 
the  front  of  the  entire  body.  Although  the  abdominal  part  of 
this  is  present  in  man  as  the  rectus  muscle,  the  thoracic  part  is 
absent,  having  been  crowded  out  of  existence,  we  believe,  by 
the  enlargement  of  the  pectoral  muscles  following  the  in- 
creased use  of  the  upper  extremities  for  prehension.  Some 
authorities  hold  that  the  sternalis,  when  present,  is  the  thoracic 
portion  of  the  rectus.     An  occasional  nerve  supply  from  the 


THE  NATURAL  HISTORY  OF  MAN  77 

intercostals  favors  this  explanation  and  indicates  the  possible 
reversionary  character  of  this  muscle. 

On  the  inner  side  of  the  lower  end  of  the  humerus  in  the 
fore  limb  of  man  there  is  occasionally  an  opening,  known  as 
the  supracondylar  foramen,  which  is  regularly  found  in  some 
of  the  lower  animals,  such  as  the  cat,  transmitting  a  large 
nerve.  The  occasional  appearance  of  this  foramen  in  man  is 
believed  to  be  a  reversion. 

At  an  early  period  of  prenatal  life  a  pointed  projection  of 
the  vertebral  column  as  a  tail  (Fig.  23)  is  quite  evident. 
During  later  development  this  projection  is  gradually  incor- 
porated within  the  body  so  that  the  terminal  part  of  the  verte- 


srt 


Fig.  27.  Supernumerary  nipples  of  man.  n,  normal  nipple; 
sn,  supernumerary  nipple.  Redrawn  from  Wiedersheim,  after 
Ammon. 


78  THE  EVOLUTION  OF  MAN 

bral  column,  the  coccyx,  which  represents  the  tail  vertebrae  of 
the  lower  animals,  no  longer  projects.  Very  rare  cases  are 
known  in  which  the  coccyx  has  remained  elongated  and  pro- 
jecting in  man,  thus  constituting  a  true  tail.  In  the  anthro- 
poid apes  this  region  is  even  more  reduced  than  in  man. 

Small  supernumerary  mammary  glands  (Fig.  27),  which  are 
not  infrequently  found  in  man,  are  reversionary  structures.  It 
is  found  that  in  early  embryonic  life,  two  rows  of  mammary 
glands  begin  to  develop  but,  unlike  the  case  of  the  lower 
mammals,  all  except  two  of  these  disappear.  Also,  at  the 
sixth  month  of  prenatal  life,  the  body  is  almost  entirely  covered 
with  fine  hair,  called  the  lanugo.  This  is  largely  shed  before 
birth  but,  in  some  cases,  it  may  persist  and  develop  in  the  adult 
to  form  a  complete  hairy  covering  for  the  body,  which  seems 
to  be  a  reversion  to  man's  ancestral  hairy  condition  such  as 
persists  in  the  anthropoid  apes. 

Thus  man's  close  kinship  with  the  anthropoid  apes  is 
strongly  suggested  not  only  by  the  fossil  forms  but  also  by  his 
natural  history.  Furthermore,  a  'blood  relationship'  is  indi- 
cated both  by  the  susceptibility  of  the  apes  to  human  diseases 
and  by  their  reaction  to  various  blood  tests,  developed  in  the 
past  few  years,  which  render  it  possible  to  distinguish  between 
human  blood  and  the  blood  of  all  other  animals  except  the  an- 
thropoid apes.  It  is  pretty  well  agreed  that  the  anthropoid  apes 
and  man  came  from  a  common  ancestor,  and  he  in  turn  from 
some  primitive,  broad-nosed  ape.  Some  believe  that  the  mam- 
mals were  evolved  from  a  primitive  reptilian  form.  Others  say 
they  came  from  the  amphibians,  which  in  turn  evolved  from  a 
fish  form,  the  .latter  from  an  invertebrate,  and  so  on  down  to 
the  protozoa.  Evolution  must  likewise  assume  that  under 
some  favorable  condition  the  earliest  living  forms  were  evolved 
from  the  inorganic  world.  Whether  such  a  process  is  going 
on  at  present  no  one  knows.  However,  the  facts  of  man's 
development,  structure,  and  variations,  which  have  been  given 


THE  NATURAL  HISTORY  OF  MAN  79 

above,  certainly  can  be  best  explained  on  the  basis  of  man's 
descent  from  lower  forms,  and  human  fossils,  as  far  as  they 
go,  as  is  clearly  shown  in  the  previous  chapter,  definitely  lead 
back  toward  a  form  from  which  both  apes  and  man  may  have 
descended. 


CHAPTER  III 

THE  EVOLUTION  OF  THE  NERVOUS  SYSTEM  OF 

MAN 

GEORGE  HOWARD  PARKER 

PROFESSOR  OF  ZOOLOGY,   HARVARD   UNIVERSITY 

The  body  of  man,  like  that  of  the  other  higher  animals, 
carries  a  full  complement  of  organs.  These  organs  are  usually- 
arranged  by  anatomists  under  some  ten  heads,  the  so-called 
organ  systems,  and  are  familiar  to  you  as  the  skeleton,  the 
muscular  system,  the  circulatory  system,  the  nervous  system, 
and  so  forth.  Although  physicians  have  been  telling  us  that 
we  normally  live  so  long  as  our  blood  vessels  last,  it  is  never- 
theless true  that  our  daily  life  is  dependent  not  upon  a  single 
system  of  organs  strictly  but  upon  the  interaction  of  all  the 
systems  that  we  possess.  No  one  system  can  be  eliminated 
without  serious  consequences.  True  we  may  have  our  tonsils 
taken  out,  our  appendix  removed,  we  may  lose  an  arm  or  a  leg, 
a  kidney,  or  even  a  lung,  but  no  one  will  give  up  with  impunity 
both  kidneys,  or  both  lungs,  or  shed  his  whole  digestive  tract. 
Death  would  be  the  inevitable  and  immediate  result.  Our 
systems  of  organs  are  so  interrelated  that  they  form  a  unified 
whole  which  justifies  the  biological  conception  of  an  organic 
individual.  The  integrity  and  continued  existence  of  such  an 
individual  is  dependent  upon  the  presence  of  at  least  the  essen- 
tial members  of  each  system.  Thus  the  organism  as  a  whole, 
to  use  a  current  expression,  is  more  than  an  assemblage  of 
parts;  it  is  an  integrated  unit. 


EVOLUTION  OF  NERVOUS  SYSTEM  8i 

The  Nervous  System  and  Personality 

Yet  when  we  examine  our  systems  of  organs,  we  find  them 
quite  differently  related  to  our  daily  activities;  the  musician 
trains  his  ear,  the  artist  his  eye,  and  the  athlete  his  muscles. 
In  this  way  each  one  develops  a  certain  individuality  or  what 
is  commonly  spoken  of  as  a  personality,  to  use  that  term  in  its 
more  modern  connotation.  In  this  sense  personality  implies 
an  outline  of  the  self,  a  resume  of  that  body  of  characteristics 
that  makes  up  an  individual  in  contradistinction  to  other  indi- 
viduals. Personality  has  commonly  been  regarded  as  an  attri- 
bute of  the  body  as  a  whole  and  yet  when  it  is  closely  scruti- 
nized, it  is  seen  to  depend  chiefly,  if  not  entirely,  upon  our 
nervous  organization. 

That  personality  has  its  seat  in  the  nervous  system  is  in  the 
main  a  relatively  modern  view.  The  ancients  for  the  most 
part  believed  that  it  permeated  the  whole  human  frame,  and 
they  located  what  may  be  called  the  attributes  of  personality 
in  the  most  diverse  parts.  Thus  Aristotle  declared  the  heart 
to  be  the  sensorium  commune  of  the  body  and,  though  he  was 
an  unusually  acute  observer,  he  was  unable  to  make  out  any 
nervous  function  whatever  for  the  brain.  Galen  believed  the 
brain  to  be  the  seat  of  the  rational  soul,  but  apparently  he  also 
accepted  the  popular  belief  that  the  heart  was  the  seat  of 
courage  and  anger,  and  the  liver  that  of  love.  Views  of  this 
kind  were  the  prevailing  opinions  among  the  ancient  writers 
and  show  that  what  we  regard  nowadays  as  personality  had 
for  them  a  most  broad  and  general  relation  to  the  body  as  a 
whole. 

Vesalius,  the  great  anatomist  of  the  sixteenth  century,  may 
be  regarded  as  the  founder  of  the  modern  belief  that  per- 
sonality is  of  strictly  nervous  origin.  In  dealing  with  the 
nervous  system  he  declares  that  just  as  the  heart  is  concerned 
with  the  vital  spirit,  and  the  liver  with  the  natural  spirit,  so 


82  THE  EVOLUTION  OF  MAN 

is  the  brain  with  the  animal  spirit.  By  the  animal  spirit,  as 
the  context  shows,  he  meant  the  capacity  to  think,  to  re- 
member, to  reason,  and  to  imagine.  All  these  functions,  how- 
ever, are  functions  of  the  brain,  and  that  body  of  reactions, 
instincts,  and  habits  that  characterizes  each  individual  whereby 
he  may  be  described  as  honest  or  dishonest,  cheery  or  somber, 
kindly  or  malevolent,  are  from  this  standpoint  products  of  the 
nervous  system.  Although  this  view  has  been  again  and  again 
assailed,  it  has  maintained  itself  to  the  present  time  and  bids 
well  to  remain  one  of  the  fundamental  facts  of  biological 
knowledge.  • 

Yet  to  the  man  on  the  street  personality  and  all  that  per- 
tains thereto  remains  much  as  in  pre-Vesalian  days,  a  vague 
general  characteristic  of  the  body  as  a  whole  and  not  a 
feature  of  one  system  of  its  organs.  To  attempt  to  persuade 
him  otherwise  is  more  likely  to  arouse  his  suspicions  than  to 
advance  his  knowledge.  This  is  particularly  true  of  so  simple 
a  matter  as  sensation.  When  you  prick  your  skin  with  a  pin 
nothing  seems  more  natural  than  to  locate  the  sensation  of 
pain  where  the  pin  abraded  the  skin  and  yet  we  know  that  the 
sensation  of  pain  is  in  the  cerebral  cortex  of  the  brain  and  not 
in  the  skin.  The  evidence  that  this  sensation  is  resident  in 
the  cortex  comes  from  several  sources.  First,  it  is  known  that 
if  a  nerve  is  cut,  the  part  of  the  body  supplied  by  that  nerve 
loses  sensibility.  When  a  nerve  going  to  a  part  of  the  hand  is 
accidentally  severed,  a  pin  may  be  thrust  into  that  part  without 
producing  the  least  sensation  whatever,  showing  that  the  hand 
in  itself  is  not  endowed  with  pain.  Not  until  the  restoration 
of  the  nerve  months  after  the  accident  does  the  sensation  of 
the  afflicted  part  return.  Not  only  are  there  circumstances 
under  which  a  part  may  be  present  though  without  sensation, 
but  there  may  be  sensations  without  the  presence  of  any  part. 
This  condition  is  well  seen  in  the  so-called  phantasmal  extremi- 


EVOLUTION  OF  NERVOUS  SYSTEM  83 

ties.  Persons  who  have  recently  lost  an  arm  or  a  leg  often 
suffer  from  very  intense  pains  apparently  in  the  missing  part. 
So  real  are  these  sensations  and  so  definitely  do  they  seem  to 
be  located  in  the  lost  member  that  it  is  often  difficult  to  per- 
suade the  patient  that  the  pains  are  not  connected  with  the  lost 
part  and  that  some  attention  to  that  part  is  needed.  Yet  the 
surgeon  knows  perfectly  well  that  these  sensations  are  caused 
by  small  tumors  on  the  cut  ends  of  the  nerves  that  formerly 
went  to  the  lost  extremity.  On  removing  these  tumors  the 
sensations  disappear.  Both  these  lines  of  evidence  show  that 
painful  sensations  though  commonly  referred  to  the  skin  are 
really  not  situated  there.  They  are  functions  of  a  more 
deeply  located  part.  When  the  central  end  of  the  system  in 
the  cerebral  cortex  suffers  destruction  either  by  disease  or  acci- 
dent, sensation  disappears  absolutely  and  completely,  a  condi- 
tion that  shows  that  the  real  seat  of  this  phenomenon  is  not  in 
the  peripheral  parts  of  the  body,  as  commonly  assumed,  but  in 
a  deep  portion  of  the  central  nervous  system. 

This  is  but  one  example  of  many  that  go  to  show  that  per- 
sonality, not  only  from  its  sensational  side  but  from  all  other 
aspects  of  its  nature,  is  a  function  of  the  nervous  system.  It 
is  not  a  quality  that  penetrates  the  human  frame  as  a  whole. 
Yet  notwithstanding  the  correctness  of  the  modern  view  as 
to  the  seat  of  personality,  the  ancient  idea  of  its  diffuse  nature 
appears  in  many  of  our  daily  habits  and  permeates  our  lan- 
guage. It  would  be  impossible  to  replace  successfully  the 
heart  on  the  February  valentine  by  the  true  organ  of  affection, 
the  cerebral  cortex,  even  though  the  convolutions  of  the  cortex 
might  be  shown  to  afford  a  much  more  subtile  means  of  send- 
ing the  hidden  message  than  the  smooth  surface  of  the  heart. 
Human  nature  cHngs  to  the  past  and  the  discarded  theories  of 
the  physicians  of  antiquity  hold  their  place  with  tenacity  in  the 
language  of  to-day. 


84  THE  EVOLUTION  OF  MAN 

The  Nervous  System  of  Man  and  Other  Higher 

Animals 

The  nervous  system  of  man  is  without  doubt  one  of  the 
most  intricate  structures  in  the  animal  kingdom.  It  is  com- 
posed of  a  most  compHcated  mechanism  of  end-stations  and 
of  intercommunicating  hnes  which  far  outruns  in  intricacy  the 
telephone  system  of  such  a  place  as  Chicago  or  New  York. 
It  is  made  of  nerve  cells,  or  neurones,  whose  processes,  the 
nerve  fibers,  stretch  like  telephone  wires  for  relatively  pro- 
digious distances  through  the  body.  When  these  neurones  are 
studied  individually  they  are  seen  to  fall  into  three  classes. 
One  of  these  classes  is  composed  of  elements  that  reach  from 
the  skin  and  other  outlying  parts,  such  as  the  organs  of  smell, 
taste,  hearing,  and  the  like,  to  the  central  organs.  These 
neurones  are  called  sensory  or  afferent  neurones.  Other 
neurones,  commonly  called  motor  or,  better,  efferent,  stretch 
from  the  central  apparatus  to  the  muscles  and  other  organs 
activated  by  the  nerves.  These  form  the  second  class.  The 
third  class,  the  internuncial  neurones,  connect  one  part  of  the 
central  nervous  system  with  another;  they  consequently  lie 
entirely  within  the  limits  of  the  central  organ  and  may  be  in 
accordance  with  their  connections  either  functionally  afferent 
or  efferent.  These  three  classes  of  neurones  make  up  the  whole 
of  the  real  nervous  substance  of  the  human  body  and  col- 
lectively they  constitute  a  system  by  means  of  which  many  of 
the  bodily  activities  are  controlled  and  in  which  take  place  such 
remarkable  operations  as  sensation,  memory,  volition,  and 
the  host  of  other  performances  which  together  constitute  per- 
sonality. 

When  we  survey  the  organization  of  the  nervous  system 
and  its  appended  parts  we  find  that,  though  it  is  made  up  of 
neurones,  the  boundaries  of  its  organs  do  not  confori^i  to  the 
limits  of  the  neurones,  but  have  a  topography  of  their  own. 


EVOLUTION  OF  NERVOUS  SYSTEM  85 

Thus  a  whole  group  of  peripheral  parts,  often  the  peripheral 
ends  of  afferent  neurones,  are  concerned  with  receiving  such 
environmental  changes  as  are  likely  to  excite  activity  in  the 
organism.  Thus  the  eye  is  receptive  for  light,  the  ear  for 
sound,  the  organs  of  touch  for  changes  of  pressure  and  the 
like.  These  organs,  commonly  designated  as  sense  organs, 
but  more  appropriately  called  receptors,  constitute  the  first 
large  class  of  parts  in  the  neuromuscular  mechanism.  The 
second  class  includes  the  central  apparatus  proper,  composed 
of  the  central  ends  of  the  afferent  neurones,  the  internuncial 
neurones,  and  the  central  ends  of  the  efferent  elements.  This  is 
the  portion  of  the  system,  corresponding  to  a  central  telephone 
station,  in  which  the  nervous  impulses  arriving  from  the  re- 
ceptors are  directed  toward  the  appropriate  channels  of  re- 
sponse and  in  which  are  stored  those  records  of  past  experi- 
ence that  modify  or  otherwise  qualify  the  subsequent  responses. 
This  second  portion  is  represented  in  man  by  the  brain,  and  the 
spinal  cord,  and  by  the  sympathetic  system  and  may  be  desig- 
nated from  one  of  its  chief  functions  as  the  adjustor  mecha- 
nism. Finally  there  is  to  be  mentioned  the  third  group  of  parts, 
not  truly  nervous  themselves,  but  under  the  control  of  the 
nervous  system,  the  muscles,  the  electric  organs,  the  glands, 
the  luminous  organs  and  the  like,  all  of  which  enable  the 
animal  to  act  in  some  particular  way  on  the  environment. 
These  have  been  appropriately  spoken  of  as  effectors  and  com- 
plete the  list  of  necessary  parts  in  the  neuromuscular  mecha- 
nism. 

A  nervous  system  composed  of  the  three  types  of  neurones 
already  mentioned  and  organized  into  receptors,  adjusters, 
and  effectors  is  characteristic  of  most  of  the  higher  animals. 
It  is  found  not  only  in  the  vertebrates  from  man  to  the  fishes, 
but  also  in  the  mollusks,  in  the  arthropods,  and  in  the  higher 
worms  such  as  the  annelids.  Even  such  a  lowly  organized 
creature  as  an  earthworm  has  a  nervous  system  developed 


86  THE  EVOLUTION  OF  MAN 

upon  this  plan.  The  so-called  brain  of  this  animal  is  a  small 
mass  of  nervous  material  lodged  in  the  dorsal  part  of  its 
anterior  end.  Connected  with  this  brain  is  a  long  segmental 
chain  of  ganglionic  enlargements  extending  along  the  ventral 
midline  of  the  worm.  These  parts  collectively  constitute  the 
central  nervous  apparatus,  or  adjustor,  for  which  the  skin  is 
the  chief  receptor  and  the  muscles  the  main  effectors.  In 
neuronic  composition  the  three  types  of  elements  already  de- 
scribed are  abundantly  represented.  Afferent  neurones  reach 
from  the  skin  of  the  worm  to  its  central  organs  from  which 
efferent  neurones  pass  out  to  its  muscles.  Internuncial  neurones 
are  also  present,  but  in  relatively  small  numbers  as  compared 
with  the  conditions  found,  for  instance,  in  the  vertebrates. 
Here  many  parts,  like  the  cerebral  hemispheres,  to  take  only 
one  example,  are  made  exclusively  of  internuncial  neurones 
whereas  in  the  earthworm  there  is  probably  not  a  single  im- 
portant nerve  center  that  is  not  entered  by  sensory  neurones 
or  which  does  not  give  rise  directly  to  efferent  neurones. 
With  this  difference,  however,  the  neuromuscular  mechanism 
of  the  earthworm  is  based  on  the  same  principles  of  construc- 
tion as  those  met  with  in  the  higher  vertebrates  including  man 
himself. 

The  Nervous  Organization  of  Sea-Anemones 

To  gain  some  idea  of  the  evolutionary  steps  by  which  such 
a  nervous  system  as  that  just  described  has  been  arrived  at,  it 
is  plainly  necessary  to  examine  the  types  of  nervous  organiza- 
tion found  among  the  lowest  of  the  multicellular  animals.  As 
a  good  example  of  these  lowly  organisms  the  sea-anemones 
may  be  selected.  Sea-anemones  are  sac-like  animals  attached 
to  rocks  or  stones,  and  provided  with  a  single  aperture  which 
leads  from  the  exterior  into  their  large  central  cavity  in  which 
digestion  goes  on  and  from  which  the  undigested  residue  is 


EVOLUTION  OF  NERVOUS  SYSTEM  87 

discharged  to  the  exterior  through  the  single  aperture  already 
mentioned  which  serves  thus  both  as  mouth  and  anus.  This 
aperture  In  almost  all  sea-anemones  Is  surrounded  by  one  or 
more  circles  of  tentacles. 

When  an  expanded  sea-anemone  is  stimulated  by  being 
touched  or  otherwise  excited  to  action,  It  commonly  responds 
by  a  quick  general  contraction,  whereby  the  seawater  contained 
in  its  digestive  cavity  Is  discharged  through  Its  mouth  and  the 
whole  volume  of  the  animal  is  greatly  reduced.  This  general 
contraction  may  be  called  forth  from  almost  any  point  on  the 
surface  of  the  animal,  showing  that  the  muscles  that  lie  within 
the  walls  of  the  creature  and  are  responsible  for  the  contrac- 
tion, are  collectively  accessible  to  nervous  Impulses  from  al- 
most every  point  on  the  surface.  This  accessibility  is*  insured 
through  the  presence  of  a  nerve-net  which  spreads  throughout 
the  living  substance  of  the  animal  and  which  brings  its  surface 
into  connection  with  almost  its  whole  musculature.  This 
nerve-net  nowhere  shows  a  special  concentration  but  extends 
rather  uniformly  throughout  the  body  and  thus  affords  an  easy 
path  over  which  Impulses  may  spread  from  the  surface  of  the 
animal  to  Its  musculature.  A  nervous  system  of  this  type  is 
commonly  called  a  diffuse  nervous  system  as  contrasted  with  a 
centralized  one  and  Is  characterized  by  the  absence  of  a  cen- 
tral organ,  or  adjustor,  through  which  all  Impulses  must  pass 
on  their  way  from  the  receptors  to  the  effectors. 

The  characteristics  by  which  a  diffuse  nervous  system  may 
be  distinguished  from  a  centralized  one  are  well  shown  in  a 
number  of  activities  exhibited  by  sea-anemones.  When  small 
fragments  of  meat  or  other  bits  of  food  are  placed  on  the 
tentacles  of  a  sea-anemone,  these  organs  wind  around  the  bits 
of  food  and,  by  bending  in  the  appropriate  direction,  deliver 
them  to  the  mouth.  If,  now,  a  distending  tentacle  on  a  quiet 
and  expanded  sea-anemone  is  suddenly  seized  at  its  base  by 
forceps,  cut  off  and  held  in  position  so  that  its  original  rela- 


88  THE  EVOLUTION  OF  MAN 

tions  to  the  animal  as  a  whole  can  be  kept  clearly  In  mind,  the 
tentacle  will  still  be  found  to  respond  to  food  brought  In  con- 
tact with  it  and  will  eventually  turn  toward  that  side  which 
was  originally  toward  the  mouth.  Thus  the  tentacle  has  within 
itself  a  complete  neuromuscular  mechanism  for  its  own  re- 
sponses and  it  is  unnecessary  that  it  should  be  connected  with 
any  general  nervous  center  in  order  to  carry  out  Its  char- 
acteristic movements.  Its  share  of  the  diffuse  nervous  system 
is  sufficient  for  its  own  needs.  How  different  this  type  of 
organization  is  as  compared  with  the  centralized  type  is  seen 
when  we  contrast  the  activity  of  the  tentacle  with  that  of  the 
leg  of  a  dog  or  the  claw  of  a  lobster  when  severed  from  the 
animal's  body.  These  parts  when  thus  cut  off  are  quite  in- 
capable of  coordinated  movement  and  show  no  evidence  what- 
ever of  the  type  of  response  that  characterizes  them  as  a  part 
of  the  whole  organism. 

Another  activity  of  the  sea-anemone  that  illustrates  the  na- 
ture of  the  diffuse  nervous  system  is  creeping.  This  operation 
is  accomplished  by  the  so-called  pedal  disc,  that  portion  of  the 
animal  by  which  it  attaches  itself  to  the  substrate.  By  means 
of  muscular  waves  that  pass  across  this  disc  the  sea-anemone 
may  creep  slowly  like  a  snail  from  spot  to  spot.  If  a  sea- 
anemone  is  cut  crosswise  in  two  and  the  upper  half  of  the 
animal  carrying  the  mouth  and  tentacles  is  thus  removed,  the 
lower  half  with  the  pedal  disc  intact  will  pucker  up  the 
wounded  surface  and  soon  creep  about  with  as  much  success 
as  the  whole  animal  did.  Here  again  the  part  concerned 
carries  within  its  own  bounds  a  neuromuscular  mechanism 
complete  for  its  needs. 

Again  if  a  sea-anemone  is  fed  from  one  side  of  its  mouth, 
it  will  take  in  by  means  of  the  tentacles  on  that  side  one  frag- 
ment of  food  after  another.  If,  now,  bits  of  meat  be  alter- 
nated with  bits  of  filter  paper  soaked  in  meat  juice,  the  two 
materials  will  be  accepted  indiscriminately  for  some  eight  on 


EVOLUTION  OF  NERVOUS  SYSTEM  89 

ten  trials  after  which  only  the  meat  will  be  taken  and  the  filter 
paper  will  be  discharged  into  the  seawater  without  being 
brought  to  the  mouth.  If,  after  having  developed  this  state 
of  affairs  on  one  side  of  the  mouth,  the  experiment  is  now 
transferred  to  the  opposite  side,  both  the  filter  paper  and  the 
meat  will  again  be  taken  in  till  this  side  has  also  been  brought 
to  a  state  of  discriminating.  Thus  the  experience  of  one  part 
of  the  animal  has  no  perceptible  Influence  on  another  in  the 
sense  that  there  is  no  common  nervous  center  where  the  experi- 
ence of  a  given  part  may  be  put  to  the  service  of  the  rest.  It  is 
as  though  we  had  to  burn  each  finger  in  turn  before  we  discover 
that  fire  is  bad  for  the  hand.  These  examples  bring  into 
strong  contrast  the  types  of  reaction  characteristic  of  the 
higher  and  the  lower  multicellular  animals  and  serve  to  illus- 
trate the  difference  between  the  centralized  and  the  diffuse 
nervous  system. 

In  a  diffuse  nervous  system,  such  as  that  possessed  by  a  sea- 
anemone,  the  external  surfaces  of  the  animal  serve  as  recep- 
tors and  these  communicate  directly  with  the  subjacent  muscu- 
lature. The  nerve-net  serves  to  spread  the  impulses  throughout 
the  body  but  without  Involving  any  central  organ.  Thus  the 
sea-anemone  may  be  said  to  possess  receptors  and  effectors 
without  an  adjustor  or  central  nervous  organ  properly  so 
called.  This  central  organ  is,  therefore,  a  feature  of  the 
higher  animals  and  in  comparison  with  receptors  and  effectors 
it  must  be  looked  upon  as  a  more  recent  evolutionary  acquisi- 
tion. Our  sense  organs  did  not  develop  in  consequence  of  a 
central  nervous  system  but  our  central  nervous  organs  devel- 
oped because  our  very  early  ancestors  had  already  acquired 
receptors  and  muscles. 

If  lowly  organized  animals,  such  as  sea-anemones,  possess 
nothing  worthy  of  the  name  of  a  central  nervous  organ,  it 
follows  that  their  so-called  sense  organs  must  differ  consider- 
ably in  function  from  those  of  the  higher  animals.     In  highly 


90  THE  EVOLUTION  OF  MAN 

differentiated  types  the  sense  organs,  the  eye,  the  ear,  the 
organs  of  touch,  of  taste,  and  of  smell,  are  concerned  with 
supplying  the  central  apparatus  with  those  elements  out  of 
which  the  intellectual  life  is  built.  This  function  must  be  en- 
tirely superfluous  in  such  an  animal  as  a  sea-anemone  where 
no  central  organ  exists.  Here  the  sense  organs  are  not  con- 
cerned with  sensations;  they  merely  excite  muscles  to  action, 
a  function  which  they  also  exercise  in  the  higher  animals. 
They  are  receptors  for  a  multitude  of  external  changes  and 
when  thus  excited  they  serve  as  triggers,  so  to  speak,  to  set 
off  the  subjacent  muscles.  Since  they  are  not  concerned  with 
sensations  they  are  more  appropriately  designated  as  receptors 
than  as  sense  Organs  and  hence  the  term  receptor,  which  is  the 
more  inclusive  of  the  two,  is  the  better  one  to  employ.  Sea- 
anemones,  therefore,  represent  a  more  primitive  type  of  neuro- 
muscular mechanism  than  the  higher  animals  do,  one  in  which 
of  the  three  organs,  receptor,  adjustor,  and  effector,  only  the 
first  and  last  are  present,  the  adjustor,  or  central  organ,  being 
a  later  acquisition. 

Sponges 

If  receptors  and  effectors  were  developed  before  adjustors, 
it  is  natural  to  ask  whether  of  these  two  parts  one  preceded  the 
other  or  did  they  both  evolve  simultaneously?  Among  the 
multicellular  animals  lower  than  the  sea-anemones,  the  sponges 
throw  light  on  this  question.  A  single  sponge  is  a  goblet-shaped 
or  finger-shaped  animal  attached  to  the  sea-bed.  Its  outer 
surface  is  covered  with  pores  which  lead  into  a  system  of 
canals  provided  with  lash-cells  by  which  the  water  is  moved 
through  the  canals  to  a  large  space  in  the  middle  of  the  sponge 
from  which  this  fluid  escapes  by  a  conspicuous  opening  at  the 
unattached  end.  From  the  current  of  water  thus  passing 
through  the  sponge  the  animal  extracts  its  nourishment  and  th 


EVOLUTION  OF  NERVOUS  SYSTEM  91 

production  and  control  of  this  current  is  one  of  its  essential 
activities. 

Many  sponges,  like  the  ordinary  bath  sponge,  are  colonial 
animals  and  consist  of  a  number  of  sponge  individuals  more  or 
less  fused  together.  In  the  bath  sponge,  which  in  its  commer- 
cial form  is  represented  merely  by  its  horny  skeleton,  the  num- 
ber of  individuals  can  be  judged  by  the  number  of  very  large 
openings  that  penetrate  from  the  outside  to  its  interior.  These 
are  usually  four,  five,  or  more  in  number  and  represent  the 
outlets  for  the  water  currents  in  the  living  sponge.  In  quite 
a  number  of  the  colonial  sponges  the  component  individuals 
are  much  more  separated  than  in  the  bath  sponge  and  rise 
from  a  common  base  as  so  many  separate  fingers.  Such 
fingered  sponges  are  very  convenient  for  study  and  are  com- 
monly of  such  a  size  as  to  admit  of  easy  experimental  treat- 
ment. 

Sponges  are  for  the  most  part  extremely  inert  and  aside 
from  a  slight  contraction  and  consequent  bending  of  the  body 
as  a  whole  they  show  very  few  activities  except  the  opening 
and  closing  of  their  pores  and  other  apertures.  In  this  way 
sponges  control  their  water  currents  and  they  accomplish 
this  partly  by  the  formation  of  protoplasmic  membranes  by 
which  the  pores  are  closed  and  partly  by  the  action  of  rings  of 
simple  muscle  cells  that  surround  the  pores,  especially  the  out- 
let openings. 

The  control  of  a  given  outlet  cannot  be  accomplished  from 
an  adjacent  finger  nor  can  it  be  brought  about  by  stimulating 
the  finger  at  the  end  of  which  the  outlet  lies  except  when  the 
stimulus  is  directed  to  the  immediate  neighborhood  of  the 
outlet  itself.  In  fact  there  is  not  only  no  experimental  evi- 
dence to  show  that  one  finger  is  connected  nervously  with 
another,  but  there  is  no  reason  to  suppose  that  parts  of  the 
same  finger  are   thus  connected.     In  other  words,  nervous 


92  THE  EVOLUTION  OF  MAN 

transmission,  such  as  is  abundantly  seen  in  sea-anemones,  seems 
to  be  completely  absent  from  sponges.  When  this  fact  is 
coupled  with  the  inability  of  histologists  to  discover  any  trace 
of  nervous  tissue  in  sponges,  it  seems  safe  to  conclude  that 
these  animals  are  devoid  of  nervous  elements  and  that  their 
muscles  are  set  in  operation  by  direct  stimulation  rather  than 
by  anything  that  may  be  described  as  a  nervous  impulse.  From 
this  standpoint,  therefore,  sponges  may  be  regarded  as 
animals  provided  with  muscles  but  devoid  of  nervous  tissue. 
They  possess  effectors  but  no  receptors  and  their  condition 
suggests  that  in  the  evolution  of  the  neuromuscular  mecha- 
nism, muscle  appeared  first  and  nervous  tissue  later,  develop- 
ing probably  in  close  proximity  to  the  previously  formed 
muscle  as  a  device  for  exciting  the  muscle  to  action. 

If  this  conclusion  is  true,  the  evolution  of  the  neuromuscular 
system  must  have  begun  with  the  appearance  of  muscle  as  an 
independent  effector,  after  which  receptors,  or  nervous  ele- 
ments to  serve  as  triggers  for  setting  off  the  muscles,  were 
added.  Finally,  between  the  receptors  and  the  effectors  a 
central  nervous  organ,  or  adjustor,  grew  up  as  the  third  ele- 
ment and  thus  completed  the  neuromuscular  system  as  exempli- 
fied in  the  higher  animals.  So  important  has  this  central  organ 
become  in  the  life  of  these  animals  that  we  scarcely  realize 
that  it  is  the  latest  addition  to  our  nervous  equipment  and  yet 
such  seems  to  be  the  case.  In  its  first  appearance  it  must  have 
been  chiefly  an  organ  of  transmission  and  intercommunication, 
a  specialized  outgrowth  of  the  more  diffuse  nerve-net.  Later 
it  doubtless  took  on  the  function  of  modifying  the  animal's 
responses  in  relation  to  its  past  and  thus  became  a  storehouse 
of  experience  and  the  seat  of  the  intellectual  life.  As  such  it 
has  reached  its  highest  point  of  development  in  the  verte- 
brates where  as  the  brain  of  man  it  is  without  doubt  the  most 
remarkable  structure  ever  evolved. 


EVOLUTION  OF  NERVOUS  SYSTEM  93 

The  Nervous  System  in  Vertebrates 

The  central  nervous  organ  of  the  vertebrate,  using  this  term 
in  the  most  limited  sense,  consists  of  the  spinal  cord  and  the 
brain.  The  spinal  cord  throughout  the  vertebrate  series  is  a 
relatively  uniform  structure,  but  the  brain  exhibits  a  strikingly 
progressive  development.  This  is  seen  especially  in  two  of  its 
parts,  the  cerebellum  and  the  cerebral  hemispheres.  Both,  but 
particularly  the  cerebral  hemispheres,  grow  immensely  in  size 
and  complication  as  we  proceed  from  the  fishes  to  man.  In 
the  lower  vertebrates  the  cerebral  hemispheres  are  concerned 
almost  entirely  with  the  sense  of  smell  and  their  cortex,  or  outer 
covering,  is  spoken  of  as  the  olfactory  cortex,  or  archipallium. 
In  the  mammals,  however,  the  hemispheres  have  reflected 
upon  them,  in  addition  to  olfaction,  practically  all  the  sensory 
activities  of  the  body  as  well  as  the  mechanism  for  the  volun- 
tary control  of  the  musculature.  These  added  parts  constitute 
the  neopallium  which  shoves  the  olfactory  archipallium  Into 
the  background.  Thus  the  neopallium  comes  to  be  the  great 
central  organ  of  the  higher  animals.  It  receives  almost  the 
whole  of  the  sensory  Inflow;  it  stores  the  impressions  of  the 
past;  and  from  It  emanate  those  impulses  that  excite  what  we 
call  our  volitions. 

It  is  a  remarkable  fact  that  in  man  the  cerebral  cortex  con- 
sists of  layers  of  nerve  cells  so  regularly  arranged  that  a  rough 
estimate  of  their  number  may  be  made.  This  Is  believed  to  be 
approximately  9,200,000,000.  This  prodigious  number  of 
cells  is  estimated  to  weigh  a  little  over  thirteen  grams  and  to 
occupy  the  space  of  less  than  a  cubic  inch.  When  it  Is  re- 
membered that  every  human  being  develops  from  an  egg  cell 
of  approximately  one  fifth  of  a  millimeter  in  diameter  and  that 
this  cell  begins  growth  by  dividing  Into  two,  and  these  two  each 
Into  two  thus  making  four,  and  then  into  eight,  sixteen,  thirty- 
two,  and  so  forth,  it  will  be  seen  what  a  stupendous  process 


94  THE  EVOLUTION  OF  MAN 

development  is  even  from  the  standpoint  of  simple  numbers, 
for  from  this  one  egg  cell  by  division  must  come  not  simply 
the  nine  billion  and  more  cells  of  the  cortex,  but  all  the  other 
countless  billions  of  cells  that  go  to  make  up  the  rest  of  the 
body.  Nor  is  this  process  of  cell  multiplication,  prodigious 
as  its  results  show  it  to  be,  the  only  remarkable  feature  in 
development,  for  it  is  also  equally  striking  that  when  the 
requisite  number  of  cells  have  been  produced,  the  operation  of 
cell  division  stops.  At  least  this  is  true  of  the  cortex,  for  here, 
as  in  a  few  other  parts  of  the  body,  the  neurones  change  very 
little  in  number  after  birth.  The  brain  cells  with  which  the 
babe  is  born  last  for  the  most  part  without  renewal  through 
mature  life  to  old  age  and  death.  What  brings  the  operation 
of  cell  multiplication  to  an  end  at  the  appropriate  moment  is 
as  little  understood  by  embryologists  as  is  the  exciting  cause  of 
the  initial  increase. 

When  it  is  recalled  that  the  9,200,000,000  cells  in  the  hu- 
man cerebral  cortex  are  the  nervous  elements  of  this  organ  and 
that  they  collectively  constitute  rather  less  than  a  cubic  inch 
of  protoplasm,  it  seems  almost  incredible  that  they  should 
serve  us  as  they  do.  They  are  the  materials  whose  activities 
represent  all  human  mental  states,  sensations,  memories,  voli- 
tions, emotions,  affections,  the  highest  flights  of  poetry,  the 
most  profound  thoughts  of  philosophy,  the  most  far-reaching 
theories  of  science,  and,  w^hen  their  action  goes  astray,  the 
ravings  of  insanity.  It  is  this  small  amount  of  protoplasm  in 
each  of  us  that  our  whole  educational  system  is  concerned  with 
training  and  that  serves  us  through  a  lifetime  in  the  growth  of 
personality. 

The  Nervous  System  and  Sex 

The  great  importance  of  the  nervous  system  for  all  that 
pertains  to  the  higher  life  of  man  cannot  be  denied  and  yet  this 


EVOLUTION  OF  NERVOUS  SYSTEM  95 

system  after  all  is  only  one  of  our  numerous  systems  of  organs 
and  lies  embedded  with  the  rest  as  part  and  parcel  of  our 
bodies.  Notwithstanding  its  unique  character,  the  nervous 
system  is  profoundly  influenced  by  its  organic  environment  and 
reflects  in  much  that  comes  from  it  the  characteristics  of  the 
body  in  which  it  lies.  This  is  nowhere  more  clearly  seen  than 
in  the  effects  which  hormones  have  upon  it.  Hormones,  as  you 
already  know,  are  substances  produced  in  the  bodies  of  the 
higher  animals  by  the  ductless  glands,  or  endocrine  organs  as 
they  are  now  called,  and  circulated  by  the  blood.  They  are 
powerful  activators  for  many  bodily  reactions  and  are  of  first 
importance  in  many  organic  activities.  Certain  hormones  have 
a  profound  effect  upon  the  nervous  system  and  consequently 
upon  personality.  In  this  respect  they  are  like  the  supposed 
humors  of  the  physicians  of  antiquity.  These  humors  were 
believed  to  be  four  in  number,  blood,  phlegm,  yellow  bile,  and 
black  bile,  and  an  excess  of  any  one  of  these  gave  a  corre- 
sponding temperament,  sanguinary,  phlegmatic,  choleric,  or 
melancholic  as  the  case  might  be.  This  idea  of  the  humors  is 
really  a  forerunner  of  the  well-established  theory  of  the  hor- 
mones, which,  however,  not  only  has  to  do  with  temperament 
but  with  many  other  functions  of  the  body.  That  materials 
introduced  into  the  circulation  have  a  profound  influence  on 
our  moods  and  other  mental  states  is  well  known  and  is  the 
basis  of  the  use  and  abuse  of  many  substances,  such  as  nar- 
cotics, alcohol,  coffee,  tea,  tobacco,  and  so  forth.  It  is,  how- 
ever, only  within  the  last  few  years  that  the  immense  impor- 
tance of  hormones  in  relation  to  the  nervous  system  has  begun 
to  be  seen.  The  hormones  concerned  are  those  that  have  to 
do  with  the  sexual  traits. 

The  great  majority  of  animals  are  either  male  or  female 
and  when  we  seek  for  a  definition  of  these  states  we  are  driven 
in  the  end  to  make  it  turn  upon  the  kind  of  reproductive  cells 
that  the  individual  produces.     Males  produce   sperm  cells; 


96  THE  EVOLUTION  OF  MAN 

females  egg  cells.  These  are  the  primary  sexual  characteris- 
tics. But  the  sex  of  the  great  majority  of  higher  animals  can 
also  be  determined  by  many  features  other  than  those  of  the 
kind  of  reproductive  cell  discharged.  Thus  in  man  the  male 
as  compared  with  the  female  is  usually  larger  in  stature  and 
more  robust,  has  hair  upon  the  face,  a  deeper  voice,  and  many 
other  features  all  of  which  go  to  mark  the  sex  as  clearly  and  as 
indubitably  as  the  primary  sexual  character  itself.  These  more 
superficial  and  obvious  distinctions  are  spoken  of  collectively 
as  the  secondary  sexual  characters  and  serve,  as  has  just  been 
intimated,  with  almost  perfect  certainty  as  an  indication  of  sex. 
If,  however,  there  is  any  ambiguity  in  this  respect,  the  final 
resort  in  a  decision  is  always  to  the  primary  sexual  characters, 
the  kind  of  reproductive  cells  produced  by  the  given  individual. 

For  a  long  time  much  interest  has  been  expressed  as  to  the 
way  in  which  the  secondary  sexual  characters  arise  and  it  is 
from  this  standpoint  that  hormones  have  come  into  much 
prominence.  Very  remarkable  experiments  in  this  direction 
have  been  recently  carried  out  by  Steinach  on  guinea  pigs  and 
rats.  The  original  object  of  this  hne  of  work  was  to  ascertain 
the  influence  of  the  sexual  glands  on  the  secondary  sexual  char- 
acters, but  the  outcome  of  it  was  the  discovery  of  a  means  of 
influencing  in  a  most  profound  way  the  sexual  life  of  an 
individual,  in  fact,  so  far  as  secondary  sexual  characters  are 
concerned,  of  converting  a  male  into  a  female  and  vice  versa. 

Steinach  removed  the  male  reproductive  glands,  the  testes, 
from  young  guinea  pigs  and,  after  they  had  recovered  from 
this  operation,  he  implanted  in  their  bodies  by  means  of  a 
second  operation  the  female  gland  or  ovary  from  a  young 
female.  The  animal  destined  by  nature  to  be  a  male  but  thus 
harboring  within  its  body  the  opposite  sex  gland  was  allowed 
to  mature,  whereat  a  most  remarkable  transformation  was 
observed.  It  developed  the  bodily  proportions  of  the  female 
in  skeleton,   hair  coat,   and  other  particulars,   its  mammary 


EVOLUTION  OF  NERVOUS  SYSTEM  97 

glands  enlarged  and  even  gave  milk,  but  what  is  perhaps  more 
remarkable  was  that  its  whole  nervous  constitution  gradually 
assumed  the  female  role.  It  became  rather  timid  and  retreat- 
ing, mothered  the  young  of  other  females  and  in  practically  all 
respects  exhibited  the  traits  of  the  female  of  its  kind.  Or- 
ganically it  displayed  practically  the  full  range  of  secondary 
female  characteristics  though  it  was  an  animal  destined  by 
nature  to  have  been  a  male. 

Steinach  also  undertook  the  conversion  of  females  into 
males  and  though  this  from  the  operative  standpoint  proved 
to  be  a  more  difficult  problem,  in  that  testes  had  to  be  repeat- 
edly introduced,  he  nevertheless  also  succeeded  in  this  en- 
deavor and  individuals  were  produced  that  though  destined 
by  nature  to  be  female  had  the  physical  and  psychical  traits 
of  males.  Such  individuals  were  aggressive  and  quarrelsome, 
and  attempted,  though  ineffectually  of  course,  to  copulate  with 
females. 

Thus  the  presence  of  a  particular  sex  gland  during  adoles- 
cence seems  to  be  the  necessary  factor  in  determining  the  type 
of  secondary  sexual  characters  that  a  given  individual  will 
show.  When  the  sex  glands  that  had  been  transplanted  in 
these  experiments  and  that  had  sojourned  in  their  new  habita- 
tion for  a  considerable  time  were  studied  histologically, 
they  were  found  to  be  considerably  modified.  The  sexual  cells 
proper  had  often  largely  disappeared  and  the  cells  that  filled 
the  spaces  between  the  groups  of  sex  cells,  the  so-called  inter- 
stitial cells,  had  often  greatly  increased.  It  is  these  cells  rather 
than  the  sex  cells  which  produce  the  hormones  that  determine 
the  secondary  sexual  characters,  and  the  sex  glands  must,  there- 
fore, be  looked  upon  as  double  in  nature.  They  produce,  first, 
the  sexual  elements,  the  sperm  cells  or  the  egg  cells,  and 
secondly,  from  another  source,  the  hormones  necessary  for  the 
development  of  the  secondary  sexual  characters.  They  are  at 
once  sex  glands  and  puberty  glands. 


98  THE  EVOLUTION  OF  MAN 

When  the  full  import  of  these  experiments  is  clearly  recog- 
nized, it  must  be  admitted  at  once  that  the  sex  glands  not  only 
control  such  secondary  sexual  characteristics  as  are  of  a  physi- 
cal nature,  such  as  bodily  proportions  and  the  like,  but  also 
those  more  subtile  features,  the  reactions,  responses,  and  in- 
stincts, which  are  equally  significant  in  defining  a  given  sex. 
These  features  collectively  have  their  origin  in  the  nervous 
system  and  since  they  are  now  known,  from  the  experiments  of 
Steinach,  to  depend  for  their  development  upon  the  sex  glands, 
it  follows  that  the  nervous  system  of  an  immature  animal  must 
be  looked  upon  as  neither  male  nor  female  but  indifferent  and 
yet  capable  of  developing  in  either  one  or  the  other  direction 
in  accordance  with  its  organic  environment. 

That  the  conclusions  to  be  drawn  from  Steinach's  experi- 
ment apply  with  full  force  to  human  beings  is  now  commonly 
admitted.  The  striking  influence  of  the  sex  glands  on  person- 
ality as  well  as  on  the  more  physical  aspects  of  the  individual 
is  well  known  to  every  surgeon  and  is  a  cardinal  point  in  his 
practice.  Yet  the  relation  of  this  simple  fact  to  human  society 
often  goes  unheeded.  Few  elements  lie  deeper  in  the  nature 
of  man  than  sex.  As  the  center  around  which  the  family  is 
built  up,  it  initiates  the  first  step  in  the  structure  of  society. 
From  this  soil  have  sprung  the  affections,  chivalry,  the  poetry 
of  love,  and  all  that  vast  array  of  literary  and  artistic  ac- 
complishment that  has  as  its  theme  man  and  woman.  And  yet 
when  the  physical  background  of  this  immense  pageant  is 
sought  for,  it  appears  to  depend  upon  the  action  of  the  inter- 
stitial secretions  of  the  sex  glands  on  plastic  nervous  organs. 
It  is  this  plasticity  that  is  both  novel  and  important,  for  it  may 
have  far-reaching  consequences  in  the  reconstruction  of  society. 
Through  it  personality  may  be  profoundly  affected,  abnormal 
states  may  be  reached  and  corrected,  and  fundamental  re- 
generations accomplished.  As  an  avenue  of  entrance  it  leads 
to  a  most  important  field  for  the  psychiatrist  and  the  social 


EVOLUTION  OF  NERVOUS  SYSTEM  99 

reformer.  Thus  the  hormones,  to  return  to  our  original  thesis, 
illustrate  how  profoundly  the  nervous  system  is  under  the  in- 
fluence of  its  immediate  organic  environment. 

The  Nervous  System  and  Organization 

If,  now,  we  picture  to  ourselves  the  evolution  of  the  nervous 
system  of  man,  we  must  imagine  the  formation  of  the  chemi- 
cal elements  from  the  electrons  of  the  stellar  laboratories,  the 
combination  of  certain  of  these  elements  into  organic  aggre- 
gates and  the  formation  of  unicellular  organisms,  the  develop- 
ment of  multicellular  types  in  whose  organization  muscles  ap- 
pear, then  receptors,  and  finally  adjustors  or  central  nervous 
organs  culminating  in  the  brain  of  man. 

Such  a  series  forms,  superficially,  a  seemingly  natural  and 
smooth  sequence  and  yet  when  it  is  examined  closely,  it  proves 
to  be  a  succession  of  breaks  and  contradictions.  The  carbon, 
hydrogen,  oxygen,  nitrogen,  and  other  elements  of  our  bodies 
act  in  a  radically  different  way  in  the  hands  of  the  chemist 
from  what  they  do  as  an  organized  part  of  our  nervous  proto- 
plasm. The  invariable  nature  of  the  chemical  reaction  is  in 
strong  contrast  with  the  fluctuating  uncertainty  of  volitional 
activity.  True,  on  repeating  what  are  intended  to  be  exactly 
the  same  processes,  the  chemist  never  gets  exactly  the  same 
results,  but  he  knows  that  the  slight  differences  he  meets  with  in 
his  work  are  errors  of  manipiilation  and  observation  and  not 
evidences  of  wilfulness  or  disobedience  on  the  part  of  the 
material  he  deals  with.  Yet  the  activities  of  these  same  chemi- 
cal elements  when  organized  into  the  children  of  his  family 
are  regarded  in  a  very  different  light  and  under  the  head  of 
personality  he  subjects  them  to  censure  and  approval  with  the 
view  of  lasting  change  and  improvement.  How  profoundly 
different  is  the  conception  of  the  activities  of  the  isolated  ele- 
ments of  our  bodies  and  of  these  same  elements  organized  into 


100  THE  EVOLUTION  OF  MAN 

parts  of  ourselves !  No  one  now  entertains  seriously  the  view 
once  put  forward  by  Haeckel  in  the  heyday  of  the  evolution- 
ary movement  that  since  human  beings  have  souls  every  atom 
of  their  bodies  must  have  part  of  such  a  soul.  The  circum- 
scribed nature  of  ordinary  chemical  action  and  the  freedom  of 
human  volition,  notwithstanding  its  elemental  background,  are 
two  different  things. 

If  the  peculiarities  of  volitional  action  are  not  to  be  dis- 
covered in  the  chemical  elements  that  make  up  the  substance 
in  which  it  occurs,  they  must  be  ascribed  to  the  organization 
of  this  substance,  that  is,  to  the  way  in  which  the  elements  of 
this  substance  are  put  together  and  interact  amongst  them- 
selves. From  this  standpoint  certain  chemical  elements  or- 
ganized as  nervous  protoplasm  have  a  greater  degree  of  free- 
dom in  their  action  than  when  the  same  elements  are  organized 
in  the  form  of  lifeless  molecules.  This  condition  may  be 
illustrated  by  a  simple  mathematical  relation.  The  ordinary 
and  invariable  type  of  chemical  reaction  might  be  likened  to 
what  would  take  place  in  a  mathematical  world  made  of  blocks 
of  fives  to  which  we  put  the  question.  What  constitutes  ten? 
To  this  there  is  only  one  answer,  namely,  two  blocks  of  five. 
The  type  of  reaction  that  is  possible  in  nervous  protoplasm  is 
like  that  in  a  world  made  of  the  digits  to  which  the  answ^ers  as 
to  what  make  ten  may  be  nine  and  one,  or  three  and  seven,  or 
any  other  of  numerous  combinations  all  equally  true.  This 
world  has  in  it  a  degree  of  freedom  comparable  to  that  in 
nervous  protoplasm  as  compared  with  the  limitations  of  the 
ordinary  chemical  reaction.  From  this  standpoint,  then,  nerv- 
ous protoplasm,  and  probably  most  other  protoplasm,  when 
considered  from  the  point  of  view  of  its  chemical  activities  has 
a  greater  degree  of  freedom  that  that  seen  in  the  ordinary 
chemical  reaction  and  in  this  characteristic  is  to  be  found  the 
possibility  of  all  volitional  performance.  That  the  properties 
and  activities  of  materials  change  with  changes  in  organization 


EVOLUTION  OF  NERVOUS  Srs¥EM         loi 

is  as  well  known  to  the  student  of  the  lifeless  phases  of  nature 
as  to  those  who  concern  themselves  with  the  so-called  organ- 
isms. The  qualities  and  activities  of  water  are  no  more  novel 
or  different  from  those  of  its  component  elements,  hydrogen 
and  oxygen,  than  are  the  qualities  and  activities  of  nervous 
protoplasm  as  compared  with  the  organic  molecules  that  make 
it  up.  Water  is  organized  hydrogen  and  oxygen  and  in  con- 
sequence of  its  peculiar  type  of  organization  it  exhibits  prop- 
erties quite  unlike  those  of  its  constituent  elements.  Thus 
water,  like  protoplasm,  differs  from  its  elements  in  conse- 
quence of  its  organization. 

It  is  sometimes  assumed  that  man  is  absolutely  untrammeled 
and  free  and  that  his  inner  life  is  without  restriction,  but  such 
is  not  the  case.  A  good  example  of  how  we  are  held  in  abey- 
ance is  seen  in  our  mental  furniture.  This  consists  of  elements, 
our  sensations,  that  reach  us  from  the  outer  world  through  our 
sense  organs.  These  elements  come  to  us  from  the  environ- 
ment and  from  nowhere  else.  We  never  invent  them  nor  in 
any  other  way  develop  them  within  ourselves.  The  mind  is 
strictly  limited  to  what  in  this  respect  is  supplied  it  from  its 
exterior.  What  may  be  done  by  way  of  freedom  and  origi- 
nality is  to  set  these  elements  in  novel  and  unusual  combina- 
tions and  it  is  in  this  way  that  the  highly  imaginative  and 
perhaps  the  insane  mind  works.  But  in  all  instances  the  ele- 
ments themselves  are  those  of  the  primitive  sensations  and  to 
such  we  appear  to  be  absolutely  limited. 

Not  only  is  the  mind  thus  limited  in  its  materials,  but  its 
processes  often  show  striking  restrictions.  This  is  illustrated 
by  the  magician's  receipt  for  turning  stone  into  gold.  Put  a 
clean  stone  into  a  pot  of  boiling  water  and  watch  it  ten  minutes 
during  which  time,  if  you  do  not  once  think  "hippopotamus," 
the  stone  will  turn  into  gold.  Needless  to  say  that  no  one  by 
this  means  has  ever  enriched  himself.  The  mind  of  man  even 
in  working  toward  its  desires  is  never  absolutely  free,  but  is 


102  THE  EVOLUTION  OF  MAN 

subject  to  restrictions  which  continually  recall  the  material 

background  on  which  it  rests. 

In  the  evolution  of  the  nervous  system  of  man  as  presented 
in  this  brief  outline  we  see  a  succession  of  steps  rather  than  a 
gradual  ascent  and  at  each  step  a  fundamental  change  suddenly 
appears,  mutation-like  in  its  character,  to  borrow  a  term  from 
the  geneticists.  Each  step  is  a  new  phase  in  organization,  but 
not  necessarily  a  change  in  the  kind  of  elementary  materials 
involved,  and  with  these  changes  in  organization  come  changes 
in  the  degrees  of  freedom  of  reaction  which  enable  us  to  bridge 
over  the  gulf  that  lies  between  the  relatively  circumscribed 
activity  in  ordinary  chemical  operations  and  the  greater  free- 
dom seen  in  the  voluntary  and  responsible  acts  of  human 
beings.  Something  of  this  view  of  the  nature  and  the  possi- 
bilities of  living  protoplasm  has  been  put  forward  by  Haldane 
under  the  name  of  organicism,  but  with  perhaps  less  reliance 
on  the  material  side  of  the  problem  than  has  been  suggested 
in  this  lecture.  Yet  interesting  and  important  as  it  is  to  push, 
to  the  extreme,  speculation  as  to  the  relation  of  our  mental  life 
to  the  materials  of  our  body,  it  nevertheless  must  be  remem- 
bered that,  with  all  our  progress,  we  are  still  not  far  from  the 
position  described  by  Vesalius  in  1543  when  he  wrote,  "How 
the  brain  performs  its  functions  in  imagination,  in  reasoning, 
in  thinking,  and  in  memory,  I  can  form  no  opinion  whatever." 


CHAPTER  IV 
THE  EVOLUTION  OF  INTELLIGENCE 

JAMES  ROWLAND  ANGELL 

PRESIDENT   OF   YALE    UNIVERSITY 

It  may  be  assumed  without  argument  that  evolution  has 
actually  occurred  within  the  field  of  intelligence,  as  it  has 
within  the  field  of  organic  structure,  and  I  shall  proceed  at 
once  to  examine  the  major  features  of  the  process.  It  will  be 
convenient  to  distinguish  in  such  an  analysis  between  the  de- 
velopment of  intelligence  in  animals  and  the  corresponding 
development  in  man.  This  distinction  is  not  for  a  moment 
intended  to  postulate  any  fundamental  difference  between  hu- 
man and  animal  intelligence,  for  this  is  one  of  the  questions 
which  can  only  be  confidently  answered,  if  at  all,  after  adequate 
examination  of  the  available  data.  It  is  simply  a  device  for 
expediting  access  to  two  great  groups  of  facts  which  present 
certain  practical  distinctions. 

In  the  field  of  cosmic  and  stellar  evolution,  we  have  such 
facts  as  are  disclosed  to  us  through  telescopic  and  spectro- 
scopic examination  of  the  heavenly  bodies,  with  their  convinc- 
ing indications  of  evolutionary  processes  extending  over  un- 
imaginable epochs  of  time  and  over  equally  abysmal  areas  of 
space.  In  the  case  of  the  crust  of  our  own  earth,  geology 
similarly  brings  to  our  knowledge  evidence  of  slow,  age-long 
changes,  as  a  result  of  which  the  present  superficial  character- 
istics of  the  earth's  surface  have  been  produced,  together  with 
its  climatic  and  other  peculiarities.    Again,  there  is  convincing 


104  THE  EVOLUTION  OF  MAN 

evidence  of  change  and  development,  of  rise  and  fall,  in  the 
tide  of  animal  life,  in  its  geographical  range,  in  its  anatomical 
organization,  and  in  its  adjustability  to  the  major  features  of 
environment.  One  of  the  lectures  in  this  series  has  in  particu- 
lar been  devoted  to  evidence  of  this  character  as  it  applies  to 
the  changes  brought  about  in  the  nervous  system  of  various 
forms  of  animal  life.  The  development  of  man  himself  and  of 
the  society  within  which  he  lives  has  also  been  passed  in  review 
and  convincing  demonstration  has  been  offered  of  the  extensive 
changes  which  have,  throughout  the  ages,  come  to  pass  in  both. 
Evolution  having  been  thus  convincingly  exhibited  in  a  number 
of  important  fields,  it  behooves  us,  in  discussing  the  present 
problem,  to  secure  impressions  as  clear  as  possible  of  the  char- 
acter of  the  evidence  upon  which  we  are  to  base  our  inferences 
and  conclusions  regarding  the  development  of  intelligence. 

Animal  Intelligence 

In  the  case  of  animal  life,  the  only  available  information  is 
to  be  gained  by  the  direct  observation  of  animal  behavior  as 
that  Is  found  among  the  creatures  surviving  in  our  age  of  the 
world.  Whether  there  may  have  been  creatures  In  the  past 
possessing  forms  of  Intelligence  substantially  different  from 
that  of  any  animals  now  living  can  neither  be  denied  nor  as- 
serted with  absolute  confidence.  But  such  evidence  as  we  have 
Is  at  least  all  against  the  inference  that  animals  superior  to 
those  now  living  have  ever  been  developed.  So  great  is  the 
similarity  of  existing  forms  to  such  extinct  forms  as  are  known 
to  us,  that  it  seems  highly  Improbable  there  should  have  oc- 
curred developments  of  Intelligence  widely  different  from  those 
represented  In  the  animal  life  of  to-day.  This  inference, 
to  be  sure,  rests  upon  the  hypothesis  which  most  scientists  re- 
gard as  conclusively  established,  to  wit,  that  intelligence  is 


THE  EVOLUTION  OF  INTELLIGENCE      105 

essentially  a  function  of  the  nervous  system  and  that  Its  char- 
acteristics vary  with  the  development  of  the  latter. 

Turning,  therefore,  for  our  clew  to  the  behavior  of  living 
organisms,  we  find  this  ranging  all  the  way  from  the  very  simple 
series  of  movements  executed  by  the  unicellular  organisms  like 
amoeba,  which  Is  quite  devoid  of  a  specialized  nervous  system, 
up  to  the  complicated  behavior  of  the  primates  and  the  phe- 
nomenal intellectual  achievements  of  man  himself.  At  once 
we  are  confronted  with  a  distinction  which,  much  transformed 
in  modern  times,  goes  back  to  the  period  of  the  earliest  specu- 
lations upon  mind  and  behavior.  All  the  early  writers  known 
to  us  stress  the  distinction  between  instinct  and  reason,  ac- 
crediting to  the  animals  Instinctive  behavior  of  a  far  more 
highly  developed  type  than  that  disclosed  in  the  behavior  of 
man,  and  assigning  to  man  powers  of  reasoning  either  wholly 
or  largely  denied  to  animals.  Modern  scientific  analysis  has 
been  disposed  greatly  to  qualify  the  rigidity  of  this  distinction. 
Man  certainly  has  a  very  definite  equipment  of  Instincts  and 
some  of  the  operations  of  animals  contain  in  them  the  begin- 
nings at  least  of  rational  conduct. 

Broadly  speaking,  actions  are  designated  Intelligent  when 
they  disclose  the  ability  to  adjust  quickly  and  successfully  to 
new  and  variable  conditions.  They  are  judged  unintelligent 
or  mechanical  when  the  same  action  is  elicited  again  and  again 
regardless  of  changes  in  the  situation  which  calls  it  forth,  or 
of  the  possibly  disastrous  nature  of  the  reaction  itself.  From 
this  point  of  view,  the  great  group  of  actions,  known  as  tro- 
pisms,  must  be  regarded  as  non-intelligent,  even  though  they 
may  at  times  benefit  their  possessors.  Here,  for  example,  is  a 
group  of  organisms  which  at  once  seek  the  darkest  corner  of 
any  area  within  which  they  are  confined.  Here  is  another 
group  which  seeks  the  lightest  place.  Again,  here  is  a  group 
which,  if  possible,  takes  up  a  position  where  the  body  may 
press,  or  be  pressed  upon  by,  surrounding  objects.    In  the  case 


io6  THE  EVOLUTION  OF  MAN 

of  such  organisms  these  tropistlc  tendencies  are  ordinarily 
responded  to  no  matter  how  untoward  the  consequences.  The 
moth  seeking  the  flame  is  a  common  exemplar  of  this  kind  of 
reaction.  And  the  biologically  undesirable  consequences  are 
plainly  exhibited  in  the  demise  of  the  performer. 

The  group  of  reactions  called  reflex  exhibit  a  similar  organic 
invariability  which,  while  generally  beneficial,  is  not  infre- 
quently disadvantageous.  In  the  human  being  sneezing,  cough- 
ing, weeping,  are  familiar  examples  of  actions  of  this  character. 
They  are  largely  outside  the  range  of  voluntary  control  and  the 
more  extreme  forms,  such  as  those  of  digestion,  are  completely 
independent  of  such  control. 

Instincts  shade  off  into  reflex  and  tropistic  reactions  by 
gradations,  which  makes  it  difficult  without  being  arbitrary  to 
draw  any  hard  and  fast  lines ;  but  they  are  in  the  higher  organ- 
isms much  less  rigid  and  fixed  than  the  tropisms  and  reflexes 
and  they  are  more  complicated  than  the  latter  because  they 
involve  a  series  of  muscular  movements,  instead  of  the  single 
movement  to  which  we  apply  the  term  reflex. 

All  this  group  of  activities,  however,  have  in  common  their 
hereditary  and  innate  character.  No  one  of  the  group  is  ever 
in  any  proper  sense  learned  or  acquired.  They  are  executed 
either  at  birth,  or  at  some  later  stage  of  the  creature's  de- 
velopment, with  a  high  degree  of  perfection  and  in  the  lower 
animals  they  are  generally  quite  rigid  and  devoid  of  any  sug- 
gestion of  intelligent  adaptation.  They  certainly  represent 
hereditary  pathways  through  the  nervous  system  over  which 
stimulations  travel  to  the  muscles  and  glands.  In  the  higher 
animals,  the  instincts  are  more  or  less  plastic  and  susceptible 
of  modification,  this  modification  in  some  cases  going  so  far 
as  to  result  in  the  complete  suppression  of  the  instinct  by 
unfavorable  environmental  conditions.  Most  of  the  instincts 
have  a  reasonably  obvious  biological  utility,  in  that  they  con- 
tribute to  the  maintenance  of  the  life  of  the  individual  or  the 


THE  EVOLUTION  OF  INTELLIGENCE      107 

species,  and  the  same  thing  is  true  of  the  reflexes  and,  pre- 
sumably, of  the  tropisms. 

Among  the  various  theories  of  the  origin  of  this  group  of 
instinctive  and  reflex  actions,  two  have  been  most  frequently 
urged.  The  one  derives  its  chief  support  from  an  examination 
of  the  supposed  facts  in  the  case  of  human  beings.  It  assumes 
that  the  expression  of  life  in  its  original  forms  was  sponta- 
neous and  indefinitely  variable.  It  further  assumes  that  some- 
thing comparable  with  volition  is  present  in  these  primitive 
spontaneous  expressions  and  that  this  volition  is  intrinsically 
intelligent,  so  that  among  the  various  spontaneous,  or  random, 
forms  of  movement  which  may  be  indulged  there  is  presently 
a  selection  of  those  which  are  most  useful  and  a  suppression  or 
elimination  of  those  which  are  harmful.  Whereupon  it  is 
further  assumed  that  these  beneficial  spontaneous  reactions^ 
become  embedded  as  fixed  habits  which  presently  are  trans- 
mitted by  heredity  to  succeeding  generations.  They  constitute 
on  this  theory  a  sort  of  frozen  intelligence.  Although  this 
view  has  been  held  in  times  past  by  scientific  men  of  eminence, 
it  is  certainly  not  looked  upon  with  favor  by  any  considerable 
number  of  contemporary  scientists.  It  makes  assumptions 
about  inheritance  which  are  almost  certainly  incorrect  and 
assumptions  about  primitive  intelligence  which  are  highly  im- 
probable. Over  against  it  is  the  view  that,  behavior  being 
essentially  a  function  of  structure,  reflexes,  instincts,  and 
tropisms  simply  represent  accidental  variations  which  have  sur- 
vived, just  as  the  variations  of  form  have  survived,  because 
they  were,  on  the  one  hand,  positively  useful,  or,  on  the  other 
hand,  sufficiently  harmless  to  permit  their  continuation,  if  only 
they  chanced  to  be  combined  with  other  reactions  of  a  pre- 
servative kind.  Both  theories  admit  that,  as  things  now 
stand,  acts  of  reflex  and  instinctive  character,  whatever  their 
evolutionary  history,  are  as  such  intrinsically  non-intelligent, 


io8  THE  EVOLUTION  OF  MAN 

non-adaptive  to  variation  in  environment.  This  is  as  true  of 
man  as  of  animals. 

Again  broadly  speaking,  it  must  be  recognized  that  the 
range  and  complexity  of  animal  instincts  bears  some  relation 
to  the  organization  of  the  central  nervous  system,  but  the  rela- 
tion is  a  highly  complicated  one.  Certain  arthropods,  for 
example,  like  the  ant,  the  bee,  the  spider,  the  wasp,  have  amaz- 
ingly elaborate  instincts,  although  the  pattern  of  the  nervous 
system  is  relatively  simple.  On  the  other  hand,  certain  of  the 
mammals  whose  nervous  system  simulates  that  of  man  himself 
are  equipped  with  instincts  of  a  seemingly  less  complicated  and 
remarkable  character.  Unequivocal  tropisms,  as  might  be 
expected,  are  generally  more  striking  and  presumably  more 
frequent  in  creatures  of  simpler  type  than  in  those  higher  up 
the  scale.  As  is  natural,  instincts  tend  to  follow  patterns  ap- 
propriate to  the  particular  environment  in  which  the  animal 
thrives.  Birds  thus  develop  nesting  instincts,  which  are  quite 
different  in  form  from  any  correlative  instincts  of  fishes.  The 
latter,  on  the  other  hand,  develop  spawning  instincts,  which 
vary  in  some  essential  particulars  from  the  reproductive  in- 
stincts of  the  birds  and  mammals.  In  discussing  intelligence 
it  is  highly  essential  to  keep  constantly  in  mind  these  inherited 
forms  of  behavior  and  to  distinguish  them  sharply  from  acts 
acquired  by  the  creature  of  its  own  initiative. 

With  this  brief  background  of  general  impressions  regard- 
ing instinctive  and  reflex  endowment  of  animals,  we  may  turn 
attention  to  their  more  strictly  intelligent  behavior.  At  this 
point  we  are  thrown  back  on  two  types  of  evidence  whose 
relative  value  is  estimated  quite  differently  by  different  scien- 
tists. We  have,  on  the  one  hand,  the  observations  of  the  out- 
door naturalist,  who  undertakes  to  describe  the  behavior  of 
animals  as  seen  under  the  typical  conditions  of  nature.  On 
the  other  hand,  we  have  the  experimental  school,  which  has 
attempted  to  study  and  analyze  the  behavior  of  animals  under 


THE  EVOLUTION  OF  INTELLIGENCE      109 

laboratory  conditions  of  control,  or  at  least  under  conditions 
of  a  somewhat  artificial  character.  Evidence  of  the  first  type 
tends  to  be  anecdotal  in  character  and,  in  the  nature  of  the 
case,  is  rarely  able  to  present  any  trustworthy  account  of  the 
life  history  of  the  individual  creature  whose  behavior  is  under 
discussion,  or  indeed  of  the  immediate  antecedents  of  the  par- 
ticular episode  under  consideration.  It  would  be  at  once 
unjust  and  ungracious  to  deny  substantial  value  to  much  of 
the  Information  emanating  from  such  sources.  Indeed,  with 
the  case  of  the  instincts  nearly  all  of  our  knowledge  derives 
from  this  source.  But  on  the  other  hand,  evidence  of  this 
character  may  be  subjected  to  the  most  searching  scrutiny,  for 
to  It  attaches  not  only  more  than  the  usual  dangers  of  inaccu- 
rate observation,  but  also  the  all  but  inevitable  tendency  to 
anthropomorphic  interpretation.  This  is  the  happy  hunting 
ground  of  the  nature  faker  and  of  the  manufacturers  of 
Arabian  Nights  tales  and  Baron  Miinchhausen  legends  of 
animal  life  and  behavior.  None  but  a  hopeless  ingrate  could 
recall  Mowgli  and  his  friends  without  a  sentiment  of  deep  and 
lasting  gratitude;  but,  if  taken  as  more  than  literary  romance, 
the  accounts  of  Kaa,  of  Shere  Khan  and  the  Banderlog,  to 
mention  no  other  instances,  can  only  result  in  profound  mis- 
apprehension. 

On  the  other  hand,  the  laboratory  school  suffers  from  the 
charge  of  subjecting  animals  to  abnormal  conditions,  under 
which  their  reactions  are  distorted  and  in  which  it  is  impos- 
sible to  expect  normal  expressions  of  their  Intrinsic  intelligence. 
As  regards  the  larger  undomesticated  animals,  there  is  doubt- 
less some  force  in  this  type  of  criticism,  and  indeed  when  it 
comes  to  certain  forms  of  procedure,  to  be  mentioned  in  an 
instant,  it  may  be  alleged  with  some  show  of  proof,  that  the 
very  conditions  under  which  the  observations  are  made  tend 
to  defeat  their  own  purposes.  For  example,  it  is  a  not  un- 
common procedure  in  animal  experimentation  to  create  in- 


no  THE  EVOLUTION  OF  MAN 

centives  to  the  solution  of  simple  problems,  either  by  creating 
strong  hunger,  or  by  the  use  of  somewhat  severe  punishment. 
In  either  case,  it  is  alleged  that  the  animal  is  thrown  into  an  ab- 
normal emotional  condition  highly  prejudicial  to  the  exercise 
of  such  powers  of  intelligence  as  it  may  possess.  Objections 
of  this  character  are  all  appreciably  less  significant  when  urged 
against  the  milder  and  less  unnatural  forms  of  experimental 
procedure  employed,  let  us  say,  in  the  case  of  simple  marine 
animals,  to  whom  can  be  given,  under  laboratory  conditions, 
surroundings  so  closely  simulating  their  native  habitat  as  pre- 
sumably to  rob  them  of  any  real  abnormality.  Moreover, 
after  every  criticism  has  been  recorded,  it  still  remains  true 
that,  when  affirmative  evidence  of  intelligent  behavior  is 
secured  under  conditions  of  experimental  control,  whether 
inside  or  outside  a  laboratory,  the  validity  of  such  evidence  is 
likely  to  be  forever  exempt  from  the  uncertainty  which  almost 
inevitably  attaches  to  the  incidental  observations  of  animals  in 
nature. 

It  is  necessary  to  direct  attention  to  these  two  main  lines  of 
attack  upon  animal  intelligence,  for  the  reason  that  observa- 
tions which  have  been  reported  from  these  two  sources  have 
often  varied  fundamentally.  The  works  of  the  outdoor 
naturalist,  for  example,  are  full  of  records  of  animal  be- 
havior alleged  to  afford  the  most  unequivocal  evidence  of 
reasoning  processes  approximating  those  of  man  himself, 
whereas  the  experimentalists  have  generally  failed  to  discern 
anything  of  this  kind  and  in  its  place  have  reported  literally 
thousands  of  instances  of  behavior  wholly  devoid  of  the  char- 
acteristic features  of  human  thinking. 

It  will  be  readily  understood  that  no  observation  of  animal 
behavior  is  likely  to  be  trustworthy,  unless  based  upon  a  wide 
and  exact  knowledge  of  the  animal's  usual  habits  of  life. 
Otherwise  one  is  exposed  to  the  error  of  interpreting  as  a 


THE  EVOLUTION  OF  INTELLIGENCE      iii 

rational  process  a  piece  of  behavior  which  may  be  partly  or 
wholly  instinctive,  or  which  may  have  been  acquired  by  wholly 
unknown  means  at  some  earlier  period  of  the  animal's  life. 

When  due  allowance  is  made  for  such  modifications  as  have 
been  already  suggested,  the  general  upshot  of  the  observations 
of  the  experimentalist  may  perhaps  be  summarized  in  this 
way.  The  very  simple  forms,  like  the  low  marine  orders, 
exhibit  a  relatively  limited  group  of  reactions,  some  of  them 
troplstic  in  character,  others,  however,  seemingly  somewhat 
variable,  but  few  of  them  suggesting  any  exercise  of  intelligent 
discrimination.  A  little  further  up  the  scale,  animal  forms  are 
encountered  which  are  equipped  with  fairly  definite  instincts 
and  which  evince  the  ability  to  learn  to  accommodate  them- 
selves to  changes  of  environment,  but  only  by  the  slowest  and 
most  tedious  processes,  giving  practically  no  indication  of  any 
trait  which  one  would  naturally  designate  intelligent.  Thus 
the  frog,  for  example,  by  earlier  observers  supposed  to  be 
entirely  incapable  of  taking  on  any  modified  reactions  by  the 
process  of  learning,  has  now,  through  the  most  patient  obser- 
vations, been  found  to  be  capable,  after  many,  many  trials,  of 
slightly  improving  his  reactions.  Granted,  for  example,  two 
pathways,  one  of  which  always  leads  to  food  and  the  other 
not,  he  can,  if  the  patience  of  the  experimenter  is  sufficient, 
ultimately  learn  to  choose  the  correct  pathway.  Still  further 
up  the  scale,  as  will  be  illustrated  in  some  of  the  lower  mam- 
malian forms,  we  get  more  positive  evidence  of  the  beginnings 
of  real  memory  and  of  a  more  definite  ability  to  modify  re- 
actions in  a  beneficial  manner,  although  this  capacity  with 
some  of  the  mammals,  such  as  the  guinea  pig,  is  almost  at  the 
zero  point.  With  others,  however,  and  particularly  with  the 
primates,  there  is  much  greater  adaptability,  and  in  a  few 
seemingly  well-authenticated  Instances  there  is  evidence  for 
something  at  least  suggesting  the  human  forms  of  inference 


112  THE  EVOLUTION  OF  MAN 

and  thinking.  This  amounts  to  saying  that  there  is  in  the 
animal  kingdom,  as  we  know  it,  the  widest  range  of  behavior 
extending  from  that  which  at  one  end  of  the  line  is  almost,  if 
not  wholly,  stereotyped  and  mechanical  to  forms  which  at  the 
other  extreme  represent  not  only  a  rich  life  of  plastic  instinct, 
but  also  highly  variable  forms  of  behavior,  some  of  which 
definitely  suggest  the  possession  of  rudimentary  intelligent 
powers.  There  is,  then,  conclusive  evidence  of  a  real  evolu- 
tionary process,  if  one  assume,  as  all  scientists  now  do,  that 
the  more  complex  organisms,  in  which  behavior  is  most 
elaborate  and  intelligent,  have  arisen  from  simpler  and  his- 
torically antecedent  forms.  That  is  to  say,  there  is  no  question 
whatever  regarding  the  wide  variety  of  the  present  modes  of 
behavior  extending  from  the  reflex  and  tropistic  type  up  to 
the  variable  intelligent  type,  and,  on  the  basis  of  the  evolution- 
ary conception  of  organic  structures,  there  can  be  no  question 
that  these  differences  in  behavior  represent  historic  evolution 
of  the  more  complex  out  of  the  simpler. 

Intelligence  and  Consciousness 

This  is  perhaps  a  convenient  point  at  which  to  mention  an 
issue  often  much  magnified  in  discussions  of  mental  evolution, 
to  wit:  Are  all  animals  conscious,  or  Is  consciousness  a  phe- 
nomenon which  appears  only  at  a  certain  stage  of  evolutionary 
development? 

Disregarding  earlier  historic  theories,  there  have  been 
three  distinct  positions  represented  by  contemporary  scientific 
opinion.  One  of  these  holds  that  all  animals  are  conscious, 
even  an  amoeba.  Indeed,  the  defenders  of  this  extreme  view 
have  sometimes  gone  further  in  maintaining  not  only  that  ail 
life,  plant  as  well  as  animal,  enjoys  at  least  a  rudimentary  form 
of  consciousness,  but  also  that  the  whole  physical  universe  Is 
but  one  aspect  of  a  reality,  which  seen  in  its  entirety  presents 


THE  EVOLUTION  OF  INTELLIGENCE      113 

a  corresponding  conscious  phase.  Needless  to  say,  we  must 
eschew  for  present  purposes  any  discussion  of  this  larger  issue. 

There  is,  second,  the  view  that  consciousness  appears  in  the 
evolution  of  the  nervous  system  at  that  point  at  which  there  is 
demonstrable  evidence  that  creatures  can  learn  to  improve 
their  reactions  on  the  basis  of  experience.  From  this  point  of 
view,  the  frog,  among  the  more  familiar  of  our  animals, 
would  represent  perhaps  the  stage  at  which  the  first  gleams  of 
intelligence  are  discernible.  Practically,  this  test  is  a  very  diffi- 
cult one  to  apply,  because  it  would  be  precarious  to  allege  with 
confidence  that,  granted  sufficient  repetitions  of  a  given  situa- 
tion, any  animals  would  fail  to  show  some  modification  in 
response.  But  purely  physical  and  chemical  reactions,  for 
example  the  formation  of  crystals  in  minerals,  exhibit  a  similar 
slow  modification.  And  yet,  in  this  case,  one  would  hardly  be 
disposed  to  allege  the  presence  of  consciousness.  Furthermore, 
where  animals  low  in  the  scale  apparently  display  adaptive 
reactions,  it  is  difficult  to  be  certain  that  the  chemical  and 
physical  stimuli  affecting  them  are  all  under  control,  so  that 
the  seeming  adaptation  may  be  accepted  as  bona  fide. 

A  third  view  holds  that  no  animals  are  conscious,  but  that 
all  their  reactions  are  essentially  of  the  mechanical  and  tropistic 
type.  One  must,  of  course,  admit  that  we  have  no  direct  access 
to  animal  consciousness,  if  such  exists,  but  the  same  thing  is 
true  of  the  consciousness  of  one's  human  neighbor. 

It  has  seemed  to  me  desirable  to  eliminate  this  whole  issue 
from  the  present  discussion,  because  we  are  primarily  con- 
cerned with  the  demonstrable  evidence  of  actions  such  as  we 
can  properly  designate  intelligent  without  regard  to  any  par- 
ticular psychic  mould  in  which  they  may  be  cast.  This  is  not 
because  the  question  is  devoid  of  interest — far  from  it — but 
because  it  does  not  lend  itself  to  profitable  discussion  within 
the  limits  of  this  article,  if  we  are  also  to  make  headway  on 
the  general  problem  of  the  evolution  of  intelligence. 


114  THE  EVOLUTION  OF  MAN 

Human  Intelligence 

How  far  the  Intelligence  of  modern  man  has  developed 
beyond  the  stages  of  the  prehistoric  man,  whose  skeletons  have 
in  recent  years  come  to  light,  It  Is  practically  Impossible  to 
state.  Certain  of  these  earliest  remains  Indicate  a  cranial 
formation  somewhat  smaller  than  that  of  contemporary  man 
and,  although  the  evidence  Is  precarious,  there  Is  perhaps  some 
ground  for  thinking  that  the  cerebral  portion  of  the  nervous 
system  was  less  highly  developed  than  now  and  that  presum- 
ably the  level  of  native  Intelligence  was  therefore  lower. 
Nevertheless,  this  would  be  merely  an  hypothesis.  If  we  turn 
to  contemporary  man,  we  find  extreme  variation  In  the  culture 
and  civilization  of  different  races,  and  a  widespread  belief  In 
equally  marked  differences  in  native  intelligence.  Thus  the 
Occidental  white  man  unhesitatingly  puts  himself  at  the  head 
of  the  list,  with  the  Asiatic  ranking  next,  American  Indians 
perhaps  next,  the  African  next,  and  at  the  bottom  possibly  the 
Bushmen  of  Australia.  This  list,  of  course,  omits  a  number  of 
important  groups,  but  may  serve  to  give  some  indication  of  a 
common  type  of  arrangement.  It  is  perhaps  needless  to  say 
that  the  Asiatic  in  making  out  his  list  would  accord  a  different 
position  to  his  own  group.  Nor  Is  any  great  racial  stock  dis- 
posed to  accept  an  inferior  status. 

The  question  which  Is  immediately  raised  by  the  most  super- 
ficial inspection  of  these  racial  differences  of  culture  and  civili- 
zation has  to  do  with  the  problem  whether  the  European  white 
man,  for  example,  has  by  virtue  of  superior  native  endowment 
passed  by  evolutionary  processes  through  stages  of  culture  and 
civilization  comparable  with  some  or  all  of  those  now  reflected 
in  the  several  racial  groups  mentioned,  or  whether  he  has  had 
an  altogether  different  history.  Have  the  civilized  races,  in 
general,  evolved  through  superior  Intrinsic  talent  out  of  the 
conditions   represented   by   savage   races?     The   problem   is 


THE  EVOLUTION  OF  INTELLIGENCE      115 

greatly  complicated  by  the  difficulty  of  separating  out  those 
factors  which  are  indicative  of  sheer  intellectual  capacity  and 
those  which  have  to  do  with  the  accidental  advantages  of  cli- 
matic or  geographic  habitat  and  the  equally  accidental  develop- 
ments of  particular  technical  or  social  practices.  It  is  easy  to 
assume  that  more  elaborate  forms  of  civilization  necessarily 
Imply  higher  intellectual  powers  and  this  is  perhaps  not  wholly 
true.  So  far  as  we  can  judge  by  the  evidence  in  historic  times, 
there  is  no  reason  whatever  to  suppose  that  the  native  intel- 
lectual abilities  of  the  average  American  citizen  are  in  any 
way  superior  to  those  of  the  Egyptians  four  thousand  years 
before  Christ,  or  the  Homeric  Greeks,  or  to  others  of  the 
peoples  of  that  general  period  in  the  Mediterranean  basin, 
records  of  whose  civilization  have  come  more  or  less  com- 
pletely to  our  knowledge.  It  would  certainly  be  a  bold  protago- 
nist who  should  assert  that  modern  European  civilization 
has  produced,  in  sheer  intellectual  power,  men  superior  to 
Democrltus,  or  Plato,  or  Aristotle,  or  Alexander,  or  Julius 
Caesar,  to  say  nothing  of  great  Orientals  like  Confucius.  In 
other  words,  since  the  period  of  historic  records  there  is  no 
convincing  evidence  of  marked  development  in  human  intelli- 
gence, despite  the  enormous  advances  made  in  the  parapher- 
nalia of  civilization;  but,  on  the  other  hand,  there  is  fairly 
definite  evidence  that  extant  human  races  differ  appreciably  in 
their  native  intelligence  and  those  which  are  living  most  nearly 
in  the  state  of  nature  which  we  believe  to  have  characterized 
the  early  history  of  our  own  racial  stock  are,  generally  speak- 
ing, marked  by  apparently  lower  general  average  intelligence 
and  by  relatively  fewer  intellects  of  high  grade.  It  seems 
therefore  a  reasonable  inference  that  the  forefathers  of  our 
own  particular  racial  stock,  could  we  but  penetrate  far  enough 
into  past  history,  would  be  found,  like  the  more  primitive 
races  to-day,  In  possession  of  somewhat  lower  degrees  of  in- 
tellectual capacity.     How  many  thousands  of  years  we  might 


ii6  THE  EVOLUTION  OF  MAN 

be  obliged  to  go  back  to  find  demonstrable  changes  it  is  impos- 
sible to  say.  We  know  that  the  major  anatomical  character- 
istics of  man  have  not  materially  shifted  for  the  last  twenty 
or  thirty  thousand  years. 

There  is  a  very  common  popular  belief  that,  although 
civilized  man  may  be  the  superior  of  his  uncivilized  contem- 
porary in  certain  forms  of  purely  intellectual  activities,  he  is 
his  inferior  in  keenness  of  sense  perception  and  in  his  response 
to  many  of  the  aspects  of  nature.  Such  evidence  as  we  have 
tends  on  the  whole  rather  to  discredit  both  of  the  Inferences 
involved  in  this  assertion  if  they  be  made  too  sweeping.  It  is 
surely  open  to  question  whether  all  races  of  nature  people  now 
living  are  radically  inferior  to  the  more  civilized  groups  in 
natural  powers  of  intelligence.  Certainly  there  are  some 
striking  individual  instances  of  high  intellectual  achievement 
attained  by  representatives  of  some  of  these  more  primitive 
racial  groups;  and,  on  the  other  hand,  there  is  good  evidence 
for  the  statement  that  at  least  occasional  representatives  of 
civilized  races  are  quite  as  keen  in  their  vision  and  hearing — 
taking  these  two  examples — as  any  of  the  primitive  peoples 
with  whom  they  may  be  compared.  The  North  American 
Indian  and  the  white  frontiersman  may  illustrate  the  point. 
There  are  not  a  few  instances  of  Indians  who  have  exhibited 
intellectual  capacities  of  a  very  high  order,  and  the  keenness 
of  vision  and  hearing  of  some  of  the  scouts  of  frontier  history 
rival  anything  reported  of  their  savage  contemporaries. 
Training  and  discipline  are  perhaps  in  both  cases  the  clew  to 
achievement  quite  as  much  as  deep-seated  and  indisputable 
difference  of  natural  capacity — a  statement  which  in  turn  must 
not  be  understood  as  implying  that  there  are  no  significant 
differences  between  the  lowest  tribes  of  savages  and  the  highest 
exemplars  of  civilization. 

If,  as  a  clever  writer  on  these  subjects  has  suggested,  we 
may  consider  existing  tribes  of  savages  as  in  some  sense  our 


THE  EVOLUTION  OF  INTELLIGENCE      117 

contemporary  ancestors,  it  is  convincingly  clear  that,  what- 
ever is  to  be  said  of  sheer  native  intellectual  capacity,  civilized 
man  has  developed  a  technique  so  superior  to  that  of  primitive 
peoples  that  his  intelligence  enjoys  enormous  advantages  at 
almost  every  stage.  It  is  peculiarly  difficult  for  us  to  dissociate 
mere  intellectual  power  from  the  cultural  surroundings  under 
which  it  is  exercised.  It  may  be,  for  example,  that  the  in- 
ventor of  the  bow  and  arrow  accomplished  quite  as  great  a 
feat  in  the  intellectual  world  of  his  day  as  the  inventor  of 
printing  in  his,  or  the  inventor  of  the  steam  engine,  or  the 
inventor  of  the  electric  light.  Similarly,  the  inventor  of  the 
fishhook  and  the  line,  as  a  method  of  extracting  food  from 
the  sea,  may  have  enjoyed  powers  of  native  intelligence  entirely 
comparable  with  those  of  our  great  modern  inventors.  All  of 
which  is  but  another  way  of  saying  that  the  evidences  of  the 
evolution  of  civilization  and  culture  are  far  more  striking  and 
far  more  demonstrable  than  those  which  suggest,  in  historic 
times  at  least,  any  real  progress  in  the  intrinsic  fabric  of  human 
thought.  Moreover,  in  all  comparisons  of  racial  groups  one 
must  remember  the  astonishing  variation  of  natural  capacity 
in  any  large  number  of  people.  The  psychological  tests  em- 
ployed in  the  American  army  during  the  war  exhibited  the 
amazing  range  of  capacity  in  a  cross  section  of  our  population. 
Certain  of  the  recruits  in  the  army  exhibited  an  intelligence 
capacity  which  marked  them  as  morons  and  accordingly  com- 
parable with  the  most  backward  races.  One  is  always  tempted 
when  comparing  one's  own  racial  group  with  another  to  take 
as  the  standard  one  of  its  very  intelligent  members.  This  is 
entirely  unfair  and  sure  to  result  in  fallacious  conclusions  unless 
one  is  in  a  position  to  select  from  the  group  under  comparison 
an  equally  exceptional  representative. 

But,  after  all  allowances  are  made,  it  would  appear  that,  if 
we  compare  the  normal  civilized  man  of  any  of  the  more  ad- 
vanced races  with  those  savages  lowest  in  the  human  scale,  the 


ii8  THE  EVOLUTION  OF  MAN 

former  is  distinctly  superior  in  the  power  of  sustained  attention 
and  thought,  in  the  range  of  things  which  interest  him,  and 
in  his  powers  of  analysis,  abstraction,  and  inference.  It  used 
to  be  alleged  that  savages  controlled  their  emotions  less 
perfectly  than  civilized  man.  Inasmuch  as  emotional  life  is 
closely  knit  up  with  instinct  and  with  the  more  primitive  and 
ancient  part  of  our  nature,  it  would  not  be  strange  were  this 
belief  true.  But  when  consideration  is  given  to  the  different 
conditions  eliciting  emotion,  it  may  be  doubted  whether  this 
conception  is  in  any  unqualified  way  correct. 

That  portion  of  the  history  of  man  marked  by  any  of  the 
evidences  of  civilization  is  so  extremely  brief,  compared  with 
the  vaster  period  of  animal  barbarism  through  which  he  must 
have  passed,  that  we  may  well  find  it  difficult  to  secure  wholly 
conclusive  evidence  of  evolutionary  change  in  his  mental 
powers.  But  such  evidence  as  there  is  all  points  to  a  great 
practical  improvement  in  the  use  of  his  native  abilities. 

When  we  contrast  the  conditions  of  savage  man  with  those 
of  any  of  the  animals,  even  the  highest  primates,  the  differences 
in  apparent  intelligence  are  very  marked.  It  would  hardly  be 
a  safe  statement  that  animals  make  no  use  of  gestures,  whether 
vocal  or  otherwise,  to  serve  the  purposes  of  a  rude  language. 
But  such  use  as  has  been  reliably  demonstrated  is  so  crude,  so 
largely  a  mere  expression  of  emotional  excitement,  that  com- 
pared with  developed  human  speech  (which  presumably  de- 
veloped out  of  emotional  expressions)  it  is  a  hopelessly  im- 
perfect tool.  Primitive  man  as  we  know  him,  although  often 
carrying  on  his  affairs  with  an  extremely  limited  vocabulary, 
nevertheless  is  able,  through  his  language  devices — to  say 
nothing  of  others — to  mark  off  and  deal  with  abstract  and  gen- 
eral relations  and  in  so  far  he  enjoys  a  technical  superiority  to 
the  animals  which,  in  effect,  is  a  difference  in  kind  as  well  as  a 
difference  in  degree.  Moreover,  broadly  speaking,  animals 
make  no  use  whatever  of  tools.     The  occasional  instance  of 


THE  EVOLUTION  OF  INTELLIGENCE      119 

the  elephant  brushing  off  flies  with  a  branch  held  in  his  trunk, 
or  the  alleged  instances  of  monkeys  using  stones  to  crack  nuts, 
are  but  sporadic  examples  of  probably  accidental  achievements 
which  in  no  case  lead  on  to  any  general  ability  to  make  use  of 
utensils  in  a  discriminating  way.  One  must  not,  in  this  con- 
nection, confuse  with  intelligent  actions  the  remarkable  in- 
stinctive manipulations  which  many  animals  are  capable  of, 
nor  the  tricks  which  they  may  have  been  taught  by  long  and 
painful  effort.  The  elaborate  nests  which  many  birds  build  are 
amazing  instances  of  utilizing  the  most  varied  materials  in 
highly  complicated  forms.  Similarly,  the  beavers  accomplish 
the  most  astonishing  results  with  the  materials  which  they 
employ  and  there  are  abundant  reports  of  their  adaptability 
to  changing  conditions  which,  if  well  established,  are  certainly 
suggestive  of  highly  intelligent  reactions.  Here  again,  how- 
ever, the  experimental  zoologist  who  has  studied  most  care- 
fully the  instinctive  activities  of  animals  will  be  most  hesitant 
to  ascribe  individual  intelligence  comparable  to  that  of  man 
in  interpretation  of  these  animal  reactions.  Certain  it  is  that, 
generally  speaking,  the  primates  are  much  more  skillful  than 
other  animals  in  adapting  themselves  to  shifting  conditions 
and  that,  even  among  them,  the  evidence  of  anything  compa- 
rable with  a  human  process  of  inference,  or  a  process  of  ab- 
stracting, or  of  generahzing,  is  very,  very  slight.  In  any  case, 
the  issue  which  is  raised  here  again  must  be  clearly  understood, 
to  wit,  that  beyond  the  adjustments  which  are  innate,  inherited, 
and  unlearned  by  the  individual  are  those  which  represent  his 
Individual  acquirement  independent  of  such  inherited  tend- 
encies.   The  latter  is  the  field  of  individual  intelligence. 

As  was  indicated  earlier  in  this  paper,  there  is  a  wide  gen- 
eral correspondence  between  the  degree  of  intelligence  mani- 
fested by  animal  forms  and  the  structure  of  the  nervous  system. 
In  particular,  intelligence  in  its  narrower  and  more  specific 
sense,  as  distinguished  from  instinct,  appears  to  be  rather  a 


120  THE  EVOLUTION  OF  MAN 

function  of  the  cerebrum  and  particularly  of  the  cortex.  If 
animals  are  arranged  in  the  order  of  the  development  of  this 
organ  in  the  nervous  system,  the  relative  size  and  complexity 
of  it  will  be  found  standing  roughly  in  parallel  with  the  variety 
and  adjustability  of  the  reaction  patterns.  That  is  to  say,  an 
animal  that  has  a  well-developed  cerebral  cortex  will  have  a 
richer  type  of  behavior,  being  less  completely  dependent  upon 
instincts  and  reflexes  and  being  capable  of  carrying  out  a  larger 
range  of  activities  than  can  an  animal  with  less  fully  developed 
cerebral  structures. 

Man  has,  as  the  great  differentiation  of  his  own  brain  from 
that  of  most  other  animals,  a  very  much  more  delicate  internal 
structure  in  the  cortex  and  relatively  very  much  larger  parts  of 
the  cortex  devoted  to  the  interconnecting  and  interrelating  of 
the  various  parts  of  that  organ  with  itself.  The  frontal  areas 
and  the  so-called  association  areas  are  relatively  very  large. 
Some  of  these  differences  are  demonstrable  only  under  the 
microscope;  others,  however,  are  obvious  even  in  the  gross 
anatomy.  But  despite  these  differences  which  are  real,  no  one 
could  ever  have  inferred  from  them  such  marked  differences  in 
the  expressions  of  intelligence  as  do  in  point  of  fact  distinguish 
man  from  even  the  most  highly  developed  animal.  The  gen- 
eral pattern  of  the  human  nervous  system  is,  broadly  speaking, 
exactly  that  of  wide  ranges  of  the  mammals  and  more  particu- 
larly of  the  primates.  Nevertheless,  the  behavior  of  man  is 
certainly  very  different  (even  though  the  difference  be  thought 
of  as  merely  quantitative  and  not  as  qualitative),  especially  on 
the  levels  of  memory,  imagination,  thought,  and  reflection. 
On  the  whole,  man's  development  and  control  over  language  is 
unquestionably  the  greatest  single  achievement  which  his  in- 
telligence has  compassed,  and  whether  one  thinks  of  it  as  cause 
or  effect,  its  presence,  more  than  any  other  one  factor,  is  re- 
sponsible for  his  enormous  superiority  to  his  animal  neighbors. 
It  has  enabled  him  to  achieve  social  cooperation  and  the  fixa- 


THE  EVOLUTION  OF  INTELLIGENCE       121 

tion  of  institutions,  to  preserve  tradition  and  modify  its 
coercive  influence  by  rational  discussion,  and  incidentally  it  has 
afforded  him  the  most  powerful  single  tool  for  creative  indi- 
vidual thinking. 

The  striking  character  of  the  difference  between  typical 
human  processes  of  inference  and  those  by  which  animals  ac- 
quire wholly  new  reactions  may  be  illustrated  by  a  single 
example.  Here  is  a  dog  shut  up  in  a  cage  with  his  food  just 
outside  the  door.  To  open  the  door  and  satisfy  his  hunger 
involves  pulling  a  cord  which  lifts  a  latch.  No  matter  how 
obvious  the  arrangement  to  human  vision,  the  dog  may  thrash 
about  for  a  long  time  in  the  neighborhood  of  the  cord,  biting 
and  clawing  the  various  parts  of  the  cage,  until  by  accident  he 
may  seize  the  cord  in  his  teeth  and  forthwith  escape.  A  human 
being  having  once  found  a  single  act  which  would  thus  open 
the  door  would  ordinarily  require  no  second  experience  in- 
stantly to  repeat  the  success.  But  the  animal  may  need  many 
such  trials  before  establishing  the  correct  response,  showing 
that  there  is  very  slow  discernment,  or  possibly  none,  of  the 
real  relation  of  the  cord  to  the  opening  of  the  door. 

Now  human  beings  do  many  things  quite  similar  to  the  ran- 
dom activities  of  the  animal  in  the  cage.  Many  a  child  at- 
tempting to  solve  a  mathematical  problem  does  exactly  the 
same  thing  and  comes  upon  the  correct  result,  if  at  all,  quite 
accidentally  and  as  the  outcome  of  a  kind  of  mental  fumbling. 
Indeed,  all  elaborate  thought  processes  inevitably  have  in  them 
much  of  this  more  or  less  haphazard  experimental  venturing. 
But  the  point  is  that  once  the  human  being  clearly  sees  the  rela- 
tion involved,  he  can  Immediately  repeat  successfully  the  pro- 
cess and  generally  carry  over  the  principle  to  other  similar  but 
not  identical  problems.  It  Is  doubtful  if  animals  ever  do  just 
this  thing.  Even  their  powers  of  imitation  are  far  less  than  is 
commonly  supposed. 

So,  despite  the  structural  similarity  of  the  brain  of  man  and 


122  THE  EVOLUTION  OF  MAN 

the  brain  of  the  higher  mammals,  the  differences  in  intelligent 
behavior  are  very  marked.  The  most  intelligent  animal  is 
probably  in  the  mental  condition  of  the  young  baby  or  the  very 
low  grade  moron,  and  this  despite  the  possession  of  instincts 
which  often  enable  the  most  astonishing  adjustments  to  en- 
vironment. 

Future  Development  of  Human  Intelligence 

One  of  the  speakers  in  this  course  raised  a  question,  which 
has  enjoyed  a  good  deal  of  attention,  and  to  which  a  further 
word  may  perhaps  be  added  in  this  connection.  Is  the  evo- 
lutionary process  at  an  end  so  far  as  concerns  the  human  brain 
and  human  intelligence?  In  the  nature  of  the  case  no  dog- 
matic reply  can  be  offered  with  confidence  and  one  must  fall 
back  upon  the  probabilities  of  the  case.  I  cannot  altogether 
sympathize  with  the  somewhat  definite  negative  opinion  occa- 
sionally advanced,  for  such  negation  has  its  chief  justification 
in  the  vast  extent  of  time  throughout  which  little  or  no  demon- 
strable advance  has  occurred  in  the  organization  of  the  human 
brain  and  therefore  presumably  in  human  intelligence.  One 
cannot  challenge  the  fact  that  for  many  thousands  of  years 
there  has  been  little  or  no  such  change ;  but,  on  the  other  hand, 
the  period  of  time  for  which  we  have  such  evidence,  twenty  or 
thirty  thousand  years,  is  so  trifling  compared  to  the  total  life 
of  the  race  and  the  total  duration  of  life  itself  on  this  planet, 
that  a  prediction  based  on  such  a  relatively  insignificant  seg- 
ment of  man's  history  seems  highly  precarious.  Assuming 
some  extra-mundane  observer  of  the  primeval  slime  out  of 
which  organic  life  has  come,  it  would  certainly  have  seemed 
to  such  an  one  grotesque  to  predict  such  changes  as  have  actu- 
ally come  to  pass,  and  particularly  as  regards  intelligence. 
Similarly  it  is  entirely  impossible  to  surmise  at  what  point 
progress  beyond  present  human  capacities  may  occur,  but  to 


I 


THE  EVOLUTION  OF  INTELLIGENCE      123 

conclude  with  any  certainty  that  such  further  progress  will  not 
occur,  much  more  that  it  cannot  occur,  seems  hardly  warranted. 
Whether  this  view  regarding  the  further  evolution  of  in- 
trinsic human  capacities  is  right  or  wrong,  there  would  appear 
to  be  no  practical  limit  to  the  changes  which  man  can  hope  to 
bring  about  in  the  conditions  of  his  life  by  the  further  appli- 
cation of  the  same  technique  which  has  produced  the  highest 
forms  of  modern  civilization,  has  produced  our  fine  arts,  and, 
particularly,  has  produced  our  modern  science.  Conceivably 
we  shall  never  have  greater  epic  poetry  than  that  of  Homer, 
greater  sculpture  than  that  of  Phidias,  greater  architecture 
than  that  of  the  Parthenon,  greater  drama  than  that  of  Shake- 
speare, greater  painting  than  that  of  Raphael  and  Titian, 
greater  symphonic  music  than  that  of  Beethoven.  There  is, 
however,  nothing  to  prevent  advance  upon  such  achievements 
and  in  the  range  of  the  natural  sciences  at  least,  thanks  largely 
to  the  perfection  of  experimental  technique  and  the  utilization 
of  mathematics,  there  seems  to  be  literally  no  limit  in  sight  to 
the  further  mastery  which  man  may  achieve  over  the  forces  of 
nature  and  consequently  no  limit  to  the  alterations  which  he 
may  be  able  to  introduce  to  the  enrichment  of  civilization. 
Even  in  the  field  of  religion,  where  obvious  evolution  has 
occurred  since  primitive  times,  the  modern  mind  has  intro- 
duced modifications  of  the  teachings  of  the  founders  of  the 
great  world  religions  designed  to  adapt  them  more  nearly  to 
the  conditions  of  contemporary  life.  The  doctrines  of  Chris- 
tianity itself,  while  based  as  truly  as  ever  upon  the  life  and 
teachings  of  Jesus,  are  undergoing  constant  development  and 
transformation  designed  to  accommodate  them  to  the  needs  of 
the  life  and  thought  of  our  time.  Strangely  enough,  the  scien- 
tific mastery  of  the  facts  of  man's  own  nature  and  the  laws 
which  control  society  linger  far  behind  the  corresponding  in- 
sight into  the  nature  of  the  processes  of  the  physical  world. 
But  surely  it  is  only  a  matter  of  time  when  these  social  sciences. 


124  THE  EVOLUTION  OF  MAN 

so-called,  will  also  have  perfected  a  technique  enabUng  man  to 
secure  mastery  over  himself  and  his  social  relations  compa- 
rable with  that  which  has  begun  in  the  control  of  physical 
nature. 

In  modern  times,  to  mention  but  a  single  point,  our  knowl- 
edge has  been  rapidly  growing  in  regard  to  the  extent  to 
which  the  mental  life  of  the  individual  human  being  is  subject 
to  influences  which  rarely  or  never  show  themselves  above  the 
level  of  his  conscious  life,  and,  even  upon  these  infrequent 
occasions,  come  so  screened  and  shrouded  that  their  real 
origin  is  seldom  understood  or  appreciated.  It  has  thus  been 
made  particularly  clear  in  the  last  century  that  man  is  in  his 
instinctive  life  close  cousin  to  the  brutes.  But  he  has  also  in 
his  nature  the  deep  grounded  tendencies  of  hundreds  of  thou- 
sands of  generations  of  savage  human  ancestors.  Further- 
more, he  carries  into  his  adult  life  many  prejudices,  fears, 
likes,  and  dislikes,  which  trace  back  to  his  own  infantile  and 
childhood  experiences.  Any  of  these  tendencies  may  well  up 
at  a  moment's  notice  to  affect  the  attitude  which  he  takes 
toward  any  issue  that  may  present  itself  in  his  hfe.  He  may 
make  a  decision  which,  with  a  not  unnatural  self-flattery,  he 
calls  a  carefully  reasoned  choice.  But  to  a  sufficiently  informed 
observer  it  would  frequently  be  revealed  that  this  reasoned 
choice  represented  an  attempt  to  justify  on  rational  grounds 
an  impulsive  preference  arising  from  some  of  these  hidden 
springs  in  human  history,  rather  than  a  wholly  disinterested 
and  unbiased  analysis  of  a  given  situation.  Moreover,  man 
at  birth  finds  himself  instantly  surrounded  with  all  the  tradi- 
tions and  practices  of  his  own  time,  race,  and  social  group, 
which  from  the  very  beginning  hem  in  his  spontaneous  activi- 
ties, furnish  the  stage  upon  which  his  instinctive  and  impulsive 
life  must  be  played,  and,  in  general,  set  boundaries  which,  how- 
ever independent,  he  can  hardly  cross.  In  point  of  fact,  the 
average  individual  is  Intensely  conservative,  indisposed  to  the 


THE  EVOLUTION  OF  INTELLIGENCE      125 

labor  and  the  hazard  of  independent  thinking,  a  creature  of 
habit,  most  content  when  most  easily  able  to  run  along  in  the 
fixed  grooves  of  daily  life  without  friction  or  annoyance. 

Nevertheless,  while  the  average  individual  may  be  intrin- 
sically indisposed  to  encourage  change,  except  in  those  circum- 
stances which  occasion  him  personally  acute  discomfort,  the 
more  active  and  progressive  minds  find  through  the  accumu- 
lated knowledge  of  the  race,  now  for  a  few  centuries  available 
in  permanent  written  form,  and  through  the  amazingly  rapid 
development  In  the  technique  of  the  sciences,  the  tools  at  hand 
for  a  literally  unlimited  evolution  In  the  actual  conditions  of 
human  life.  From  this  practical  point  of  view,  therefore,  the 
evolution  of  intelligence  may  be  considered  as  close  to  its 
beginnings  rather  than  in  any  sense  drawing  near  to  its  close. 


CHAPTER  V 
SOCIETAL  EVOLUTION 

ALBERT  GALLOWAY  KELLER 

PROFESSOR  OF  THE  SCIENCE  OF  SOCIETY,  YALE  UNIVERSITY 

The  essence  of  evolution  is  the  development  of  form  out  of 
form,  in  a  connected  series,  with  survival  of  the  fitter  forms 
in  adjustment  to  environment.  The  outcome  of  evolution  is 
adjustment  of  life  to  life-conditions.  No  informed  person 
feels  any  longer  the  need  of  arguing  the  truth  of  the  theory; 
interest  now  centers  in  the  extension  and  correction  of  knowl- 
edge as  to  the  details  of  the  process,  and  in  the  applications 
of  the  truths  discovered.  In  the  Darwinian  theory  of  adjust- 
ment we  have  one  of  those  widely  orienting  factors  which  array 
knowledge  in  orderly  vistas  and  lead  mankind  to  believe  that 
there  is  some  sense  in  earthly  existence. 

If  there  is  any  one  place  rather  than  another  where  man- 
kind would  like  to  find  sense  and  order,  it  is  in  the  field  of 
human  social  relations.  No  one  can  read  the  vivid  pages  of 
Henry  Adams's  Education  without  a  deeper  appreciation 
of  the  darkness  and  deviousness  of  the  ways  along  which  all 
of  us  are  traveling,  though  most  of  us  are  not  so  conscious  and 
concerned  about  our  gropings  as  was  that  anxious  and  rueful 
searcher  after  enlightenment.  Adams,  an  evolutionist  believes, 
was  after  too  much.  He  wanted  to  find  some  norm  of  prog- 
ress in  human  history,  and  seems  to  have  renounced  high  hopes 
of  Darwinism  when  he  found  that  it  offered  no  such  norm. 

It  is  one  of  the  common  misconceptions  about  evolution,  and 


SOCIETAL  EVOLUTION  127 

one  Into  which  Adams  fell,  that  it  means  progress.  It  means 
adjustment  only.  Such  adjustment  seems  to  be  progressive  if 
it  leads  in  a  direction  which  we  choose  to  call  forward;  but  it 
may  appear  also  to  be  retrogressive  If  its  runs  counter  to  that 
direction.  To  us  the  change  from  the  flint-lock  to  the  per- 
cussion-cap musket  seems  a  progressive  adjustment,  and  the 
return  from  the  latter  to  the  former,  in  hot  and  damp  regions, 
where  the  cap  deteriorated  while  the  Imperishable  flint  did 
not,  appears  to  be  retrogression.  Both  were  expedient  ad- 
justments to  life-conditions. 

We  ought  not  to  be  dismayed  at  the  sight  of  forces  operat- 
ing In  what  seem  to  us  opposite  ways,  at  one  and  the  same  time. 
We  should  not  bemoan  the  failure  of  evolution  because  motion 
is  not  always  visibly  In  the  direction  we  like  or  expect,  any 
more  than  we  should  despair  of  gravitation  because  it  causes 
both  the  stone  to  fall  and  the  balloon  to  rise.  The  fact  is  that 
the  terms  progress  and  retrogression,  as  their  etymology  indi- 
cates, imply  that  the  user  of  them  has  selected  some  center  of 
operations  from  which  he  can  infallibly  adjudge  what  is  "pro'' 
and  what  is  "retro."  He  Is  at  liberty,  in  free  countries,  to  do 
this  for  himself  and  to  try  to  persuade  others  that  he  is  right ; 
and  sometimes  whole  groups  can  agree  on  what  is  progress 
and  what  is  not;  but  it  Is  generally  impossible  to  get  extended 
unanimity  as  to  the  identity  of  "forward"  and  "backward." 
Especially  Is  this  the  case  when  It  comes  to  the  appraisal  of 
social  relations.  Institutions,  and  policies. 

But  this  whole  difficulty  Is  escaped,  in  the  case  of  evolution, 
If  we  consent  to  view  that  process  as  It  is,  and  do  not,  in  our 
straining  after  the  assessment  of  things  as  progressive  or 
retrogressive,  hug  to  ourselves  the  misconception  that  evolu- 
tion and  progress  are  synonymous.  If  we  simply  ask,  concern- 
ing any  organic  or  social  form,  whether  It  is  an  adjustment, 
past,  present,  or  pending,  we  shall  all  find  ourselves  in  a  sub- 
stantial agreement  that  will  permit  of  our  going  along  farther 


128  THE  EVOLUTION  OF  MAN 

together.  I  myself  think  the  protective  tariff  to  be  a  case  of 
retrogression,  but  that  does  not  prevent  me  from  agreeing  with 
its  many  ardent  and  even  candid  sponsors  that  it  is  an  im- 
portant adjustment  to  life-conditions.  I  regard  the  League  of 
Nations  as  the  only  practical  and  working  proposition  in  the 
field  of  international  relations;  others  think  it  a  fooHsh  and 
retrogressive  measure;  but  all  of  us  could  agree  that  it  is  a 
widely  accepted  adjustment,  now  under  test.  Slavery  was  once 
an  adjustment  that  everyone  believed  in.  The  time  came  when 
conditions  changed  and  there  arose  a  difference  of  opinion  as 
to  whether  it  was  good  or  bad,  progressive  or  retrogressive. 
Now  it  has  come  to  be  regarded  as  a  maladjustment.  But, 
whatever  the  judgment  upon  it  at  various  times,  anyone  can 
see  that  it  has  been  one  of  the  ways  into  which  men  naturally 
fell  in  meeting  the  conditions  of  life  as  presented. 

I  have  used,  perhaps,  a  disproportionate  amount  of  space 
in  seeking  to  enforce  this  point;  but  I  have  done  so  de- 
liberately, because  there  is  no  other  range  in  which  people  are 
so  wont  to  set  up  private  and  local  standards,  upon  which 
they  then  assess  all  things,  as  they  are  in  the  range  of  social 
life.  If  many  are  disposed,  petulantly  or  dismally,  to  despair 
of  organic  evolution  because  it  does  not  support  their  ideas  of 
progress — which  it  never  set  out  to  do,  any  more  than  it  adver- 
tised to  explain  the  origin  of  life — how  much  more  darkly 
would  they  despair  of  a  social  evolution  that  lays  no  claim  to 
be  progressive.  Man's  dearest  Interests  are  vitally  involved 
in  his  social  life;  in  fact,  what  discouraged  Adams  and  others 
with  Darwinism  was  not  its  givings  in  the  organic  field,  but 
its  fallings-short,  in  promise,  of  their  hopes  in  the  social  field — 
into  which  it  was  speedily  and  incontinently  dragged  by  the 
almost  Instinctive  tendency  to  ^'reason  from  analogy." 

I  cannot  go  into  this  last  matter — of  how  conclusions  were 
drawn  concerning  the  nature  and  life  of  human  society  from 
the  nature  and  life  of  organisms.    It  was  partly  Darwin's  fault 


SOCIETAL  EVOLUTION  129 

for  embarking  upon  the  discussion  of  social  and  moral  matters, 
in  the  Descent  of  Man;  matters  concerning  which  he  was 
little  better  informed  than  any  other  non-specialist.  It  was 
still  more  the  fault  of  Spencer,  who  became  so  enamored  of 
the  analogy  between  organism  and  society  that  he  came  almost 
to  believe  it  an  identity.  Then  the  Germans  got  hold  of  it  and 
constructed  huge  volumes  of  uninspired  muddlement  about  the 
"structure  and  life  of  the  social  body." 

The  analogy  between  a  society  and  an  organism  is  a  pretty 
one,  as  developed  by  Spencer.  Its  development  was  not  with- 
out use.  But  of  what  use?  It  is  of  no  use  at  all  in  proving 
anything  about  society.  An  analogy  is  no  proof  of  anything. 
Consider  the  exhorter  who  described  the  life-cycle  of  the 
butterfly  and  wound  up  triumphantly:  "Now  who  shall  say 
that  there  is  no  proof  of  immortality!"  Proof  demands  facts, 
ever  more  facts,  all  sorts  of  facts  bearing  on  the  subject.  Out 
of  them  comes  the  theory,  and  from  them  the  theory  is  cor- 
rected and  re-corrected.  It  is  most  essential  that  the  facts 
shall  not  be  selected,  either  to  be  acclaimed  or  to  be  ignored. 

An  analogy,  on  the  contrary,  is  a  specially  selected  fact  or 
relation.  It  is  picked  out  of  many  possibilities  because  it  is 
thought  most  vividly  to  set  forth  some  idea  already  developed 
and  fixed  in  mind.  It  is  not  the  search  for  truth  that  the 
analogy-user  is  after;  it  is  the  exposition  of  a  position  already 
taken.  Analogy  is  perhaps  the  most  effective  device  for  exposi- 
tion; but  it  is  the  tool  of  the  preacher,  not  of  the  discoverer. 
Its  supreme  effectiveness  is  found,  probably,  in  the  parables  of 
Christ,^  who,  in  trying  to  transmit  spiritual  truths  to  simple 
minds,  took  recourse  to  homely  analogies  on  all  sides. 

There  can  be  no  direct  "reasoning  from  analogy,"  there- 
fore. People  who  write  on  social  evolution  are  regularly 
charged  with  trying  to  do  that,  and  generally  justly;  perhaps 
if  a  writer  starts  out  by  saying  that  it  cannot  be  done,  it  will 

1  For  example,  Matt,  xiii.,  31,  33. 


I30  THE  EVOLUTION  OF  MAN 

be  believed  by  some  of  his  readers  that  he  Is  not  endeavoring 

to  do  It. 

But  the  analogy,  correctly  understood  and  not  burdened 
with  a  weight  It  cannot  carry,  can  perform  a  service  of  great 
value.  If  In  one  field  of  Investigation  (say  the  organic)  we 
know  that  certain  phenomena  are  produced  In  a  certain  way, 
and  if  in  an  adjacent,  less  understood  field  (say  the  social)  we 
find  analogous  phenomena,  we  are  justified  by  long  experience 
in  the  inference  that  the  unknown  producing  factors  in  the  new 
field  are  probably  similar  to  the  known  ones  In  the  older  range. 
If,  in  particular,  we  find  adjustments  In  the  organic  field  pro- 
duced by  the  so-called  Darwinian  factors,  and  If  we  discover 
that  the  social  range  shows  social  forms  representing  adjust- 
ments to  the  life-conditions  of  society.  It  Is  reasonable  to  Infer 
that  the  factors  producing  social  adjustments  may  be  similar 
to  those  producing  organic  adjustments.  This  is  the  more 
likely  in  view  of  the  fact  that  all  members  of  human  society 
are  organisms,  so  that  the  two  ranges — of  organic  and  of 
social  life — are  not  merely  contiguous,  but  Interpenetrative. 
If  organic  forms  are  evolved  by  the  action  of  the  Darwinian 
factors  of  variation,  selection,  and  heredity,  their  joint  action 
resulting  in  adjustment  to  life-conditions,  it  is  a  hint  to  us  that, 
in  default  of  any  more  promising  lead,  we  had  better  look  for 
counterparts  of  the  Darwinian  factors  In  the  social  range. 

This  suggestion  has  been  unreflectingly  and  unconsciously 
adopted  In  popular  usage.  It  is  seen  that  habits  and  customs 
are  passed  on  from  generation  to  generation  somewhat  as 
bodily  qualities  are.  It  Is  necessary  to  use  some  term  to  cover 
the  process.  The  biological  term  Is  heredity.  It  Is  easier  to 
catch  up  a  term  In  use  than  to  Invent  a  new  one.  Hence 
writers  speak  of  "social  heredity."  It  Is  like  speaking  of 
"brass  andirons."  However,  it  is  vaguely  realized  that  habit 
and  custom  are  not  transferred  by  actual  heredity,  through  the 
germ-plasm;  and  the  perception  of  the  unanalyzed  difference 


SOCIETAL  EVOLUTION  131 

involved  is  indicated  by  the  adjective  "social" — not  plain 
"heredity,"  but  "social  heredity."  The  upshot  of  the  matter 
is  that  even  the  casual  observer  has  noted  the  likeness  between 
things  social  and  things  organic  and  biological. 

It  seems  to  me  that  we  had  better  take  this  hint  from 
analogy  and  work  on  it.  Evolution  is  proved  and  accredited 
in  the  organic  field;  at  Darwin's  centenary  scientists  of  all  de- 
scriptions united,  in  a  volume  called  Darwin  and  Modern 
Science,  in  bearing  witness  to  the  fruitful  suggestion  received 
by  them  from  the  Darwinian  theory.  We  had  better  see 
whether  that  theory  can  not  help  us  in  discovering  some  order 
and  sense  in  social  phenomena.  I  think  it  has  helped  some  of 
us  in  just  that  way.  Our  courses  in  the  science  of  society, 
representing  the  best  we  have  to  give  to  our  students,  have  for 
many  years  begun  with  the  effort  to  make  sure  that  they  all 
secure  a  layman's  knowledge  of  organic  evolution. 

My  predecessors  in  this  course  of  lectures  have  shown  that 
the  evolutionary  process  does  not  stop  short  of  man  as  an 
animal.  Huxley,^  in  comparing  him  with  the  anthropoids, 
summarizes  as  follows:  "Thus,  identical  in  the  physical  pro- 
cesses by  which  he  originates — identical  in  the  early  stages  of 
his  formation — identical  in  the  mode  of  his  nutrition  before 
and  after  birth,  with  the  animals  which  lie  immediately  below 
him  in  the  scale, — man,  if  his  adult  and  perfect  structure  be 
compared  with  theirs,  exhibits  ...  a  marvelous  likeness  of 
organization.  He  resembles  them  as  they  resemble  one 
another — he  differs  from  them  as  they  differ  from  one 
another."  But  if  man  is  thus  similar  to  the  animals,  it  would 
appear  that  he  must  come  under  the  same  need  of  physical 
adjustment  to  life-conditions.  If  so,  he  should  show  differ- 
ences comparable  to  those  exhibited  by  animals  as  the  result 
of  adjustment  to  widely  diverse  life-conditions.  Being  the 
most  widely  ranging  of  all  animals,  he  might  be  expected  to 

2  Huxley,  T.  H.,  "Man's  place  in  nature,"  1901,  p.  83. 


132  THE  EVOLUTION  OF  MAN 

show  the  greatest  physical  diversities.  He  does  not.  Does 
this  mean  that  evolution  stops  short  of  man?  Let  us  first  get 
some  of  the  facts  before  us. 

Human  beings  are  much  alike  over  both  time  and  space. 
For  many  thousands  of  years  man  has  been  substantially  the 
same  kind  of  a  physical  being  as  he  is  to-day.  Over  all  the 
earth  he  is  pretty  much  the  same  sort  of  animal.  One  who 
has  followed  the  efforts  of  scientists  to  distinguish  the  varieties, 
or  races,  of  mankind  can  realize  how  essentially  alike  they  are. 
Conviction  of  this  essential  similarity  has  led  to  the  assertion 
that  "man  is  unchanged  in  a  changing  environment."  But  this 
seems  to  mean,  on  the  face  of  it,  that  somewhere  during  the 
course  of  human  development  evolution  is  suspended;  for  evo- 
lution Is  adjustment  to  environment. 

Certainly  mankind  has  encountered  widely  diverse  environ- 
ments. Men  live  in  countries  where  the  temperature  falls  far 
below  zero ;  also  where  it  rises  considerably  over  one  hundred 
degrees  Fahrenheit.  They  Inhabit  regions  which  are  cold 
and  dry,  cold  and  damp,  hot  and  dry,  and  hot  and  damp. 
They  live  at  sea-level  or  thousands  of  feet  above  it.  They 
persist  where  there  is  much  animal  life  of  all  kinds,  or  where 
there  Is  little  of  any  kind.  Of  all  animals  the  most  widely 
distributed  over  space,  men  have  encountered  all  varieties  of 
earthly  environment.  Yet  they  are  essentially  alike.  The 
most  widely  distributed;  the  least  changed — "unchanged  In  a 
changing  environment." 

Through  time  also,  with  Its  secular  and  often  radical 
changes  of  life-conditions,  alteration  In  man's  physical  make-up 
has  been  relatively  sHght.  Animals  adjust  even  to  so  regular 
and  recurrent  a  set  of  conditions  as  the  succession  of  the  sea- 
sons, while  man  has  remained  practically  the  same  through 
the  protracted  ups  and  downs  of  centuries  and  millenia.  Is 
it  possible  that  the  evolutionary  process  is  stayed  and  that  man 
is  exempted  from  It?     Of  course  it  Is  not  halted;  and  he  is 


SOCIETAL  EVOLUTION  133 

not  exempt.  The  process  merely  changes  its  mode.  It  is  no 
longer  evolution  of  the  organic  type,  resulting  in  structural 
adjustment;  it  is  evolution  of  another  grade,  resulting  in 
another  sort  of  adjustment.  There  must  be  adjustment  just 
the  same,  as  a  condition  of  existence.  Evolution  goes  on  as 
long  as  adjustment  to  immutable  life-conditions  goes  on — that 
is,  as  long  as  life  lasts.  It  is  this  typically  human  phase  of 
evolution  which  we  want  to  identify  and  examine. 

When  human  beings  get  into  a  situation  (a  cold  climate,  for 
instance)  which,  for  animals,  evokes  physical  adaptation  (such 
as  a  thicker  coat),  we  find,  perhaps,  some  small  adjustment 
by  way  of  bodily  change ;  but  typically  and  generally  what  we 
see  is  the  employment  of  materials  external  to  the  body — skins, 
wood,  metal — which  are  interposed  to  form  the  instruments 
of  adjustment.  It  takes  a  certain  brain-action  to  arrive  at 
such  utilization  of  the  things  available  in  nature.  When  bees 
build  combs,  it  is  by  an  instinct  that  represents  a  single  adjust- 
ment, once  and  for  all,  whereas  man  has,  in  the  brain,  a  sort 
of  specialized  adjustor  capable  of  being  turned  upon  this  and 
then  upon  that  situation.  His  brain  is  somewhat  like  one  of 
these  tool-handles  which  include  in  one  instrument  the  possi- 
bility of  a  variety  of  operations,  except  that  the  brain  is  in- 
finitely more  protean  in  its  transformations. 

The  brain  clothes  its  adjustments  in  material  form.  They 
are  thus  realized  or  made  real — materialized,  or  rendered  in 
terms  of  matter — externalized,  or  worked  out  in  things  ex- 
ternal to  the  body.  Every  such  realized  thought  is  a  piece  of 
culture  or  of  the  apparatus  of  civilization.  Such  are  the 
climbing-irons  of  the  linesman,  which  are  the  cultural  counter- 
part of  the  natural  climbing-foot;  such  is  the  aeroplane,  as 
compared  with  the  wings  of  the  bird.  Tools,  weapons,  houses, 
parachutes — all  these  are  objects  of  material  culture  which  are 
counterparts  of  what  nature  has  developed  over  countless  ages 
of  organic  evolution — for  the  beaver,  whose  tools  are  teeth; 


134  THE  EVOLUTION  OF  MAN 

for  the  stag,  whose  weapons  are  hoofs  and  horns;  for  the 
nautilus,  whose  house  is  his  shell;  and  for  the  dandelion  seed, 
which  sails  about  on  its  supporting  structure. 

But  not  all  these  cultural  products  are  made  of  substances. 
They  are  often  immaterial  forms  of  organization  and  conduct. 
Specialization  of  labor  is  a  cultural  adjustment  for  readier  self- 
maintenance,  saving  as  it  does  time,  effort,  and  material,  and 
yet  winning  to  a  better  product.  Marriage  is  a  cultural  ad- 
justment by  which  two  very  differently  endowed  sexes  get 
along  together  and  rear  young.  Government  is  a  cultural 
adjustment  resulting  in  orderly  and  peaceful  human  relations. 
All  economic,  political,  and  other  social  systems,  economies, 
and  institutions  are  cultural  adjustments  to  life-conditions  of 
maintenance  and  sex,  and  of  others  presented  to  men  in  their 
earthly  life.  Good  government  is  as  much  a  favorable  adjust- 
ment as  is  the  web  foot  of  a  duck,  and  polygamy  is  as  obsolete 
an  adjustment  for  us  as  five  toes  came  to  be  for  the  horse. 

If  this  is  so,  the  fact  of  adjustment,  and  the  need  of  it,  is 
as  patent  in  the  case  of  mankind  as  it  is  in  that  of  other 
animals  or  of  plants.  Only  it  is  attained,  in  the  former  case, 
by  factors  not  precisely  the  same  as  in  the  latter.  We  shall 
come  to  these  factors  presently.  The  outstanding  fact,  thus 
far,  is  that  plant  and  animal  adjustments  are  typically  physical, 
while  human  adjustment  is  typically  not  physical.    It  is  mental. 

It  is  also  social.  Civilization  is  the  product  of  numbers  and 
the  contact  of  numbers.  The  new  invention,  representing  a 
better  adjustment  to  life-conditions,  say  the  gas-engine,  never 
springs  full-fledged  out  of  the  brain  of  any  individual.  The 
one  who  gets  the  credit  for  it  is  at  best  but  the  last  of  a  long 
line  of  experimenters,  who  has  added  the  finishing  touch — 
where,  indeed,  he  is  not  the  exploiter  who  merely  appropriates 
the  results  of  a  long  series  of  labors  in  which  he  has  borne  no 
part.  Much  less  did  any  individual  invent  marriage  or  prop- 
erty, though  tradition  sometimes  accredits  them  to  a  mythical 


SOCIETAL  EVOLUTION  135 

law-giver.  To  arrive  at  any  of  these  cultural  adjustments  de- 
mands the  give  and  take,  and  the  gradual  accumulation,  pos- 
sible only  where  there  are  a  number  of  human  beings  cooperat- 
ing in  the  effort  to  maintain  and  perpetuate  the  race,  that  is, 
in  a  society.  Cultural  adjustment  is  therefore  social;  or, 
better,  since  the  word  ''social"  is  so  vague,  it  is  "societal." 
It  is  a  thing  that  occurs  only  in  society.  It  is  "of  society,"  and 
that  is  what  "societal"  means.  The  securing  of  such  cultural 
adjustment  is,  therefore,  by  "societal  evolution." 

This  is  the  new  mode  or  grade  of  evolution  that  replaces  for 
man  the  organic  mode  or  grade.  Organic  evolution  goes  but 
a  short  way  in  explaining  human  relations,  even  though,  since 
man  remains  always  an  animal,  it  is  basic  to  the  whole  of 
human  existence.  Natural  selection  continues  to  operate  upon 
men,  for  instance,  through  the  ravages  of  some  diseases;^  but 
in  general  it  is  replaced  by  another  kind  of  selection  which  may 
be  called  societal.  Natural  selection  could  never  result  in  a 
religious  adjustment,  for  example.  Such  an  adjustment  is  not 
of  the  organic  grade.  At  best,  natural  selection  cannot  exceed 
that  grade ;  in  fact,  it  is  a  risky  contention  to  assert  that  even 
the  fittest  human  animals  are  surviving  and  multiplying  in  com- 
parison with  the  unfit.  The  alarmists  about  race-suicide, 
counter-selection,  racial  degeneration,  and  the  like,  are  com- 
plaining that  we  are  breeding  all  the  time  from  the  worse  ele- 
ments in  the  population.  We  may  be,  if  animal-fitness  is  the 
sole  criterion;  and  we  may  be,  even  though  we  realize  that 
there  are  other  criteria.  But  it  is  essential  to  note  that  societal 
fitness — fitness  to  be  a  member  of  society — is  not  identical  with 
physical  fitness.  It  is  enlightening  to  run  over  a  list  of  those 
men  who  have  served  society  best  and  see  how  many  of  them 
were  physically  defective. 

If  natural  selection  is  not  effectively  in  operation  in  pre- 
serving the   fittest  human   animals,  because   societal  criteria 

8  Holmes,  S.  J.,  "The  trend  of  the  race,"  1921,  chs.  VIII  and  IX. 


136  THE  EVOLUTION  OF  MAN 

always  cut  across  organic  criteria,  it  is  certainly  out  of  its  range 
when  it  comes  to  institutional  development.  If  we  read  that 
cannibalism  or  feudalism  has  perished  by  "a  sort  of  natural 
selection,"  the  very  qualification  in  the  phrase  indicates  that 
the  user  of  it  is  merely  employing  an  analogy.  We  are,  I 
repeat,  upon  another  plane  of  evolution  where  the  processes 
and  survival-values  are  somewhat  altered  from  those  existing 
in  nature.  The  attempt  to  carry  natural  selection  over  to  the 
new  plane  is  wholly  unproductive. 

It  is  understood,  then,  that  evolution  in  the  societal  range 
is  of  a  different  kind,  quality,  brand,  or  variety  from  that 
operating  in  nature.  Societal  adjustments,  we  go  on  to  infer, 
are  probably  produced  by  the  operation  of  factors  present  in 
the  organic  field,  though  these  factors  must  needs  be  somewhat 
metamorphosed  in  their  manifestations  in  the  societal  range. 
To  one  who  has  in  mind  such  considerations  as  the  foregoing, 
there  is  nothing  to  do  but  to  try  out  the  Darwinian  factors 
upon  societal  phenomena.  But  upon  what  shall  he  try  them? 
Of  course,  upon  the  aforesaid  cultural  adjustments:  inven- 
tions, systems,  economies,  organizations,  and  the  rest.  Are 
these  societal  adjustments,  like  the  structural  ones  of  plants 
and  animals,  the  end-results  of  variation,  selection,  and  hered- 
ity, operating  in  their  societal  modes  and  manifestations? 

A  great  many  of  the  cultural  adjustments  are,  as  we  see 
them  in  institutional  form,  as  in  marriage  or  religion,  im- 
mensely complex.  It  is  expedient  to  seek  them  in  their  simpler 
phases,  just  as  one  would  reduce  a  complex  fraction  in  order  to 
be  able  to  handle  it.  The  simplest  form  of  all  societal  institu- 
tions is  custom.  They  all  come  out  of  it.  Custom  is  also  a 
conception  difficult  to  handle  because  it  is  all-pervasive  and 
eludes  the  grasp.  It  required  a  sort  of  tour  de  force  to  seize, 
define,  and  thus  reduce  to  usable  form  this  elusive  and  floating 
conception.     This  was   done   by  my  predecessor.   Professor, 


SOCIETAL  EVOLUTION  137 

Sumner.*  I  am  bound  to  say  that  he  did  not  give  much  atten- 
tion to  the  possibility  of  extending  evolution  into  the  societal 
field  ;**  but  he  furnished,  in  any  case,  the  necessary  basis  for 
such  an  enterprise.  We  shall  review  his  findings  in  their  salient 
aspects.® 

When  the  first  societies  of  which  we  know  appear  to  view, 
they  are  already  provided  with  a  set  of  ways,  or  a  traditional 
procedure,  by  which  they  carry  on  self-maintenance,  and  every 
other  of  their  activities  as  well.  These  ways  represent  a  con- 
currence of  group-members  in  the  practice  of  expedients,  eco- 
nomic, political,  religious,  or  other,  which  have  been  proved 
to  them,  in  the  event,  to  be  successful  ones.  These  expedient 
ways  have  been  called  the  folkways  or  mores.  Language  is 
one  of  the  most  typical  of  the  mores;  division  of  labor  is 
another.  No  one  planned  them,  but  they  grew  up  and  are 
practiced  unquestioningly,  unconsciously,  and  automatically. 
They  correspond  to  habits  in  the  individual.  Taken  all  to- 
gether, they  constitute  the  code  of  behavior  in  a  society.  They 
represent  the  proper  way  to  act,  and,  even  though  they  are  not 
subjected  to  any  rational  or  critical  examination,  there  exists 
the  conviction  that  they  are  the  only  right  ways,  the  only  ones 
fit  to  live  by.  The  mores,  says  Sumner,  are  "the  popular 
usages  and  traditions,  when  they  include  a  judgment  that  they 
are  conducive  to  societal  welfare,  and  when  they  exert  a  coer- 
cion on  the  individual  to  conform  to  them,  although  they  are 
not  coordinated  by  any  authority."  It  is  just  as  well  to  have  a 
technical  term  for  them,  for  they  are  not  precisely  customs,  or 
social  habitudes,  or  ethics,  or  morals. 

They  become  uniform  and  universal  in  a  group,  and  also 
imperative ;  and,  often  over  long  periods,  they  are  so  resistive 

*  Sumner,  W.  G.,  "Folkways,"  etc.,  1907. 
6  Cf.  Keller,  A.  G.,  "Societal  evolution,"  1915,  pp.  328-330. 
®  Certain    of    the    following    paragraphs    a;re    a    reproduction    of    Keller, 
A.  G.,  "Through  war  to  peace,"  1918,  parts  of  chs.  VI  and  XVIII. 


138  THE  EVOLUTION  OF  MAN 

to  change  as  to  appear  invariable.  Many  of  them  are  strongly 
sanctioned  by  religion;  in  fact,  practically  all  of  them  that  are 
of  long  standing  are  supported  by  the  readiness  of  the  spirits, 
ancestral  or  other,  to  punish  infringement  or  alteration.  They 
thus  come  to  form  a  prescribed  body  of  rules  of  behavior  for 
life  in  society  that  well  deserves  the  title  of  "the  social  code." 

Within  the  range  of  societal  self-maintenance,  the  mores 
determine  how  the  struggle  for  existence  and  the  competition 
of  life  shall  go  on,  thus  rising  to  meet  and  cope  with  certain 
vital  and  perennial  life-conditions.  Another  inescapable  and 
vital  life-condition  is  laid  down  in  the  bisexuality  of  the  human 
race;  there  are  the  relations  of  the  sexes  to  be  ordered,  in  the 
interest  of  the  society's  well-being.  Innumerable  mores  attend 
upon  the  association  of  man  and  woman,  parents  and  children, 
and  they  work  out  into  various  forms  of  marriage  and  the 
family.  A  big  group  of  mores  always  surrounds  some  vital 
condition  of  society  life,  like  that  of  sex,  and  forms  the  ap- 
proved method  of  dealing  with  it.  Another  such  condition,  for 
further  example,  was  felt  in  the  vividly  conceived  presence  of 
a  world  of  ghosts  and  spirits,  an  imaginary  environment  to 
which  men  adjusted  themselves  by  the  unplanned  development 
of  a  set  of  mores  covering  forms  of  avoidance,  exorcism,  con- 
ciliation, and  propitiation  of  spiritual  beings. 

But  these  several  sets  of  mores,  "mere  custom"  at  first, 
gradually  attained  a  stage  of  organization  where  they  became 
institutions,  as,  for  example,  matrimony  or  religion.  There 
is  no  human  institution  that  has  not  risen  from  the  matrix  of 
custom;  the  rise  of  new  institutions,  now  as  always,  is  out 
of  the  same  prolific  source.  And,  as  they  take  more  definite 
form  and  somewhat  disengage  themselves  from  the  mass  of 
custom,  the  institutions  do  not  lose,  but  carry  with  them,  that 
approval  and  that  conviction  as  to  their  indispensability  for 
welfare  that  were  accorded  to  the  mores.  Anything  that  is  in 
our  mores  is  right,  and  so  our  institutions  are  the  best.    "The 


SOCIETAL  EVOLUTION  139 

mores,"  says  Sumner,  again,  "can  make  anything  right  and 
prevent  condemnation  of  anything."  They  are  the  approved 
ways  of  meeting  the  conditions  of  living,  and  are  developed, 
accepted,  and  practiced  without  much  intervention  of  reasoned 
purpose. 

They  are  to  a  society  what,  for  example,  density  and  color 
of  fur  are  to  arctic  animals ;  namely,  automatic  adaptations  to 
environment.  Life-conditions  are  present  and  society  has  to 
live  under  them.  This  is  rendered  possible,  or  easy,  or  easier, 
by  adjustments  in  the  manner  of  life  or  ways  of  living.  Thus 
we  have  a  societal  code  characteristic,  for  instance,  of  the 
arctics  or  of  the  tropics,  of  isolation  or  accessibility,  of  over- 
population or  under-population,  of  the  country  or  of  the  city, 
of  peace  or  of  war. 

With  this  understanding  as  to  the  nature  of  custom,  the 
lowest  terms  of  all  of  society's  institutions,  and  knowing  that 
customs  and  institutions  are  adaptive  to  life-conditions,  we  are 
now  to  inquire  whether  there  are,  acting  upon  the  mores, 
forces  which  are  the  counterparts  of  those  productive  of  adap- 
tation in  the  organic  range.  Are  variation,  selection,  and 
heredity,  or  factors  which  are  their  counterparts  in  the  form 
of  evolution  typical  of  human  society,  present  and  active  in 
the  field?    If  so,  what  is  their  mode  of  operation? 

The  factor  that  leads  off  in  any  evolutionary  process  is  varia- 
tion. Without  it  all  would  be  uniformity,  equality,  and  change- 
lessness.  The  existence  of  variation  in  custom  and  in  custom- 
born  institutions  is  evident  to  anyone;  demonstration  of  its 
presence  would  consist  in  an  endless  rehearsal  of  obvious 
detail. 

Variation  in  the  mores  represents  a  series  of  tentatives,  de- 
parting more  or  less  from  the  accepted  code,  that  are  struck 
out  upon  by  individuals  in  the  pursuit  of  their  interests.  The 
individual's  function  is  that  of  an  agency  for  variation.  These 
slight  departures  from  the  code  are  in  evidence  all  the  time;  in 


I40  THE  EVOLUTION  OF  MAN 

fact,  the  society's  code  is  a  sort  of  average  or  mean  or  type, 
about  which  cluster  the  codes  of  classes,  sects,  and  other  larger 
and  smaller  sub-groups.  The  individual  may  adhere  to  a  num- 
ber of  these  sub-groups,  as  his  interests  dictate.  He  may 
belong,  for  instance,  to  the  miners'  union,  the  Baptist  church, 
the  Socialist  party,  the  Masonic  lodge,  at  one  and  the  same 
time.  When  interests  change,  other  and  new  codes  may 
appear,  some  of  them  departing  widely  in  character,  perhaps, 
from  the  general  or  typical  code  of  the  society  at  large.  In 
general,  the  rise  of  such  variations  is  a  consequence  of  dis- 
comfort under  the  prevailing  code;  interests  strain  toward  a 
better  realization  by  way  of  change,  small  or  great. 

It  is  to  be  noted  that  variations  upon  customs  and  institu- 
tions may  exhibit  a  high  degree  of  rationality.  They  may 
represent  true  experimentation,  because  they  may  be  set  forth 
consciously  and  deliberately,  after  intensive  study  of  situations 
and  of  societal  laws,  with  the  intention  of  securing  more  ex- 
pedient adjustment  of  society  to  its  life-conditions.  But  they 
come  to  nothing — they  do  not  get  into  the  mores — unless  there 
is  general  concurrence  in  them.  They  remain  stillborn  unless 
verification  is  immediate,  concrete,  and  positive.  Rational 
variations — new  details  in  the  program  of  adjustment — are 
presented  in  every  age.  Whether  they  are  adopted  or  not  is 
another  matter,  for,  as  we  shall  see,  there  is  not  much  of  the 
rational  in  the  selective  process,  except  as  the  latter  is  seen, 
in  retrospect,  to  have  worked  out  expedient  adjustments 
through  the  action  of  human  agencies  inspired  by  the  most 
diverse  and  often  irrelevant  motives.  If  deliberate  and  plan- 
ful  action  enters  anywhere  into  the  process  of  societal  evolu- 
tion, it  is  in  connection  with  variation;  for  variation  is,  as  we 
have  seen,  very  much  in  the  competence  of  individuals,  and  it 
is  the  individual,  not  the  crowd,  that  will  occasionally  be  found 
to  think  in  terms  of  society. 

Among  these  variations,  whatever  their  provenance,  selec- 


SOCIETAL  EVOLUTION  141 

tion  takes  place.  Such  variations  may  be  short-lived  and  ex- 
hibited by  only  a  few,  or  there  may  be  a  concurrence  of  many 
which  carries  them  forward  until,  perhaps,  the  code  of  the 
society  at  large  has  been  profoundly  modified.  Some  of  the 
variations  live  and  some  die  out.  Here  is  the  fact  of  selection. 
All  through  history,  codes  and  institutions  have  appeared, 
have  persisted  for  a  time,  and  have  been  altered  or  have 
passed  completely  away.  But  the  process  of  societal  selection 
is  somewhat  involved.  I  should  prefer,  for  the  moment, 
merely  to  record  its  presence. 

The  remaining  factor  is  heredity.  It  Is  clear  enough  to 
anyone  that  the  mores  are  not  inherited  but  learned — acquired 
anew  by  each  generation.  Language  is  the  best  example :  men 
have  used  it  time  out  of  mind,  but  no  one  is  ever  born  with 
a  command  of  it.  Mores  are  also  passed  over  from  one  group 
of  adults  to  another.  Hence  heredity  is  not  present  in  the 
societal  range.  But  there  is  something  there  which  discharges 
essentially  the  same  function  and  is  a  genuine  counterpart. 
Without  variation,  we  have  seen,  all  would  be  monotony  and 
changelessness;  but  without  heredity  or  some  factor  similarly 
conservative,  all  would  be  chaos  and  discontinuity.  Even 
social  life  is  not  altogether  that;  and  it  is  not  that  because  in  it 
too  there  operates  a  conservative  factor. 

Transmission  of  the  mores  is  by  tradition.  What  matter 
if  its  channels  are  through  the  eye  and  ear,  and  not  by  way 
of  the  germ-plasm?  Tradition,  like  heredity,  tends  to  repeat 
the  type.  It  is  brought  about  through  imitation,  either  spon- 
taneous or  induced.  Spontaneous  imitation  is  a  natural  ac- 
tivity, common  to  animals  and  man,  and  especially  marked, 
among  human  beings,  in  the  young.  The  receiver  of  the  mores, 
thus  transmitted,  wants  to  receive,  and  takes  the  initiative  in 
the  transfer,  as  when  the  small  boy  apes  his  father.  But  such 
acquisition  is  also  capable  of  being  induced,  where  there  is  no 
likelihood  that  it  will  be  spontaneous,  by  precept  and  disci- 


142  THE  EVOLUTION  OF  MAN 

pline.  This  is  education,  in  its  broadest  sense.  The  receiver 
may  be  indifferent  or  even  unwilling  to  receive,  and  the  giver 
commonly  takes  the  initiative,  as,  for  example,  in  the  "uplift- 
ing" of  a  "lower"  race.  Also,  while  spontaneous  imitation 
carries  all  the  mores  indiscriminately,  education  carries  a  more 
or  less  wisely  selected  body  of  mores.  It  is  clear  that  the 
former  is  the  more  natural,  elemental,  impersonal,  spontaneous, 
and  automatic  process;  the  latter  is  effective  as  it  succeeds  in 
reproducing  the  essentials,  at  least  in  semblance,  of  the  former, 
but  in  comparison  it  appears  artificial.  It  involves,  it  has  been 
noted,  an  antecedent  choice  or  selection  from  the  main  body 
of  the  mores:  we  will  teach  the  young  certain  things,  and 
others  we  will  try  to  keep  from  them  as  long  as  possible.  This 
choice  is  supposed  to  be  a  reasoned  and  purposeful  one;  but 
such  a  selection  has  little  of  the  sureness  and  severe  correct- 
ness of  an  automatic  selection. 

These  evolutionary  factors  are  operative  in  the  life  of  every 
society,  from  the  family  group  to  the  nation.  And  they  do  not 
stop  there.  They  are  effective,  on  the  grand  scale,  in  the  life 
of  human  society  as  a  whole.  There  is  a  world-code  that  has 
been  in  process  of  formation  with  the  establishment  of  prox- 
imity between  the  nations;  for  that  proximity,  brought  about 
by  the  annihilation  of  distance,  has  meant  altered  conditions 
of  life  for  many  societies;  and  variations  that  have  been  dem- 
onstrated, under  selection,  to  be  expedient,  have  been  trans- 
mitted until  enough  mores  have  come  to  be  held  in  common 
by  all,  or  nearly  all,  to  justify  the  term  "international  code" 
or  "world-code."  Variations  around  this  code,  or  in  departure 
from  it,  may  now  be  originated  by  a  whole  nation,  and  sub- 
mitted for  world-wide  acceptance  or  rejection.  Slavery,  for 
example,  has  been  rejected,  while  democracy  has  widened  its 
range.  And  of  late  has  stood  forth  Germany,  as  champion  of 
a  code  that  is  still  undergoing  the  ordeal  of  selection.  These 
national  variations  on  the  world-code  cannot  be  tested  up  as 


SOCIETAL  EVOLUTION  143 

soon  as,  or  shortly  after,  they  appear — as  Mormonism  was 
tested  up  on  the  American  national  code — and  the  process  of 
selection  is  the  more  imposing  when  it  comes.  We  turn  now  to 
a  survey  of  the  essentials  of  the  selective  process. 

It  is  about  the  factor  of  selection  and  its  operation  that  the 
students  and  experts,  genuine  or  alleged,  in  the  social  sciences, 
are  at  considerable  variance.  Few  would  dispute  the  opera- 
tion of  variation  and  transmission;  hence  I  have  reserved  the 
contentious  topic  of  selection  for  special  consideration.  And 
first  let  us  be  clear  as  to  what  "selection"  means.  The  ordi- 
nary use  of  the  word  conveys  the  idea  of  picking  out  some- 
thing desirable  or  good  from  a  collection  of  things  not  so  good 
or  not  so  desirable.  Such  a  conception  of  selection  is  a  posi- 
tive one.  But  that  conception  ought  not  to  be  carried  over  to 
color  either  natural  selection  or  societal  selection.  The  truth 
of  it  is  that  it  is  the  unfit  animals  and  plants  which  are  selected 
— for  death — and  it  is  incidental  to  that  process  that  we  have 
a  "survival  of  the  fittest."  It  is  the  inexpedient  custom  that  is 
selected — for  disappearance — and  it  is  incidental  to  that  even- 
tuality that  the  more  expedient  custom  or  institution  survives. 
The  useful  conception  of  selection  is  therefore  a  negative  one. 
If  one  does  not  get  this  firmly  into  his  head,  he  is  likely  to  be 
looking,  in  the  primitive  way,  for  some  benign  or  malign 
agency  where  only  impersonal  natural  or  societal  law  prevails. 

To  attain  to  selection  there  is  need  of  struggle  and  competi- 
tion. It  is  not  by  discussion  nor  by  guesswork  nor  by  soulful 
yearning  that  the  relative  speed  of  several  runners  is  settled; 
it  is  by  a  race.  In  nature  there  is  the  struggle  for  existence, 
and  plant  or  animal  forms  succumb  under  it.  Well,  the  life 
of  societies  also  has  been  characterized  by  perennial  struggle. 
It  is  sometimes  to  the  death,  and  under  such  circumstances 
the  selection  is  sharp  and  decisive,  as  it  is  in  nature.  Again, 
however,  failure  in  the  societal  struggle  is  not  visited  by  such 
dire  penalties.     Competition  between  societies  runs  all  the  way 


144  THE  EVOLUTION  OF  MAN 

from  wars  of  annihilation  to  rivalries  in  things  of  the  spirit. 
The  degrees  of  intensity  of  selection  among  the  mores  corre- 
spond to  the  degrees  of  violence  and  decisiveness  in  this  com- 
petition. 

The  ultimate  form  of  societal  selection — one  from  which 
there  is  no  appeal — is  the  war  of  annihilation.  It  was  the 
tribunal  before  which  all  the  earhest  and  most  important 
collisions  in  societal  policy  were  settled.  War  is  still  the  court 
of  last  appeal  when  all  milder  forms  of  settlement  have,  as  in 
the  year  19 14,  failed.  It  is  not  supposed  to  involve  annihila- 
tion nowadays,  though,  as  the  popular  fancy  noted,  the  treat- 
ment accorded  Belgium  and  northern  France  savored  of  Attila 
the  Hun. 

Of  course  the  mores  do  not  fight  each  other,  though  we  say, 
figuratively,  that  Protestantism  fought  Catholicism,  or  that 
there  is  a  warfare  between  religion  and  science.  It  is  not  the 
codes  of  mores  that  fight;  it  is  the  men  practicing  the  codes 
who  do  that.  But  the  codes  rise  and  fall  with  the  successes  of 
their  sponsors  in  the  competition.  If  a  tribe  that  practices 
cannibalism  comes  into  collision  with  another  which  abhors 
the  custom,  and  is  overcome,  there  is  not  likely  to  be  much 
anthropophagy  in  that  region  for  some  time.  For  even  if 
the  conquered  cannibals  are  not  massacred,  but  enslaved,  they 
lose,  along  with  their  power,  their  self-determination  in  the 
matter  of  their  code.  I  think  it  will  be  clear,  upon  reflection, 
that  great  wars  generally  issue  in  so-called  "new  eras,"  "new 
worlds,"  or  "new  dispensations,"  which  mean  new  codes  of 
adjustment. 

In  the  course  of  time  the  minor  collisions  of  codes  have 
come  to  be  settled  without  much  or  any  bloodshed.  Enlight- 
ened states  refuse  to  concern  themselves  much  about  the  reli- 
gious beliefs  of  their  constituent  groups,  where  once  execution 
and  persecution  were  rife.  Revolutions  have  been  tamed  down 
into  elections.     Commercial  and  industrial  warfare  is  carried 


SOCIETAL  EVOLUTION  145 

on  at  the  polls.  Ballots  replace  bullets.  But  selection  goes  on 
just  the  same,  so  long  as  there  is  a  competition,  with  winners 
and  losers.  Bagehot^  has  an  important  chapter  on  the  "Age 
of  Discussion,"  from  which  it  appears  that  the  voice  and  the 
pen  have  somewhat  ousted  the  sword  in  the  settlement  of 
codes  and  policies. 

This  is  not  the  place  to  go  fully  into  the  various  forms  taken 
by  societal  selection.  It  is  plain  enough,  however,  that  there 
are  plenty  of  them.  It  is  only  because  they  are  so  much  a 
matter  of  course,  being  registered  daily  in  the  press  for  anyone 
whose  attention  has  been  called  to  their  bearing  upon  societal 
evolution,  that  it  sometimes  comes  as  a  shock,  especially  since 
we  are  nourished  so  largely  upon  romance  and  phantasms,  to 
see  that  competition  is  always  the  indispensable  precondition  to 
development.  If  we  think  we  have  got  on  since  primitive 
times,  we  may  set  it  down  to  the  diversities  produced  by  varia- 
tion and  shown  up  in  the  incessant  conflicts  between  men  ad- 
hering to  their  differing  codes.  There  is  no  fault  to  be  found 
with  the  effort  to  minimize  the  tragedies  of  competition  by 
setting  up  rules  of  the  game ;  but  those  who  dream  of  universal 
equalization,  communalization,  and  pacification  are  proposing 
to  abandon  the  agencies  which  have  brought  us  from  savagery 
to  the  civilization  which  we  now  acclaim. 

The  recurrent  dispute  about  societal  selection  is  as  to 
whether  or  not  men  deliberately  plan  out  and  realize  society's 
destiny.  The  plants  and  animals  are  supposed  by  most  people 
to  be  under  the  sway  of  a  vast  force  which  they  can  in  no  way 
control ;  natural  selection  is  thought  to  operate  over  them  and 
to  determine  their  destiny,  as  it  were,  from  without.  So  far  as 
they  are  concerned,  they  seem  to  be  totally  unconscious  of 
what  is  going  on,  and  have  no  say  about  their  own  destiny. 
But  men  do  not  like  to  believe  that  about  themselves,  nor  about 
the  nation  to  which  they  belong,  nor  even  about  the  human 

7  Bagehot,  W.,  "Physics  and  politics,"  1902,  ch.  V. 


146  THE  EVOLUTION  OF  MAN 

race.  They  like  to  think  that  a  people  chooses  its  paths  and 
policies,  and  consciously  and  purposefully  advances  toward 
some  selected  end.  They  make  much  of  what  might  be  called 
a  rational  selection  by  a  people  between  codes  and  policies  pre- 
sented to  them  for  adjudication.  The  country  is  figured  as 
thinking  things  out  for  the  country's  welfare,  as  sifting  evi- 
dence and  being  intellectually  persuaded  as  to  this  and  that. 
It  seems  to  be  assumed  that  '^he  people"  can  think  in  terms 
of  a  nation  and  will  form  a  public  opinion  that  operates  as 
intelligent  self-direction. 

Most  of  this  sort  of  contention  is  myth-making,  like  the 
philosopher's  picture  of  the  ''noble  savage" — he  never  having 
seen  one.  Perhaps  some  rare  statesman  may  rise  to  the  power 
of  thinking  in  terms  of  high  generality;  but  it  is  at  his  peril, 
at  least  during  his  lifetime,  that  he  tries  to  realize  those 
thoughts.  Lofty  talk  is  appreciated,  but  action  on  the  basis 
of  wide  generalization  is  repellent,  as  "unpractical"  or  "ideal- 
istic." Long  after  his  death,  such  a  statesman  may  get  a 
statue ;  but  that  will  be  in  consequence  of  the  verdict  of  history, 
arrived  at  when  the  heat  and  passion  have  died  down. 

What  moves  men — the  masses  of  men,  whose  numbers, 
social  bulk,  and  formidable  inertia  are  commonly  left  out  of 
adequate  account  by  theorists — is  not  thought,  but  emotion. 
And  what  sets  emotion  going  is  interest.  And  the  circle  of 
interest  is,  for  most  men,  very  narrow  and  very  closely  drawn 
around  one's  self.  What  sets  the  revolutions  in  motion,  with 
the  result  of  drastic  selection  in  the  codes,  is  not  the  cerebration 
of  anyone  over  great  issues,  but  the  unendurable  discomfort 
and  awakened  emotions  of  the  masses.  Their  interests  have 
been  so  outraged  that  anything  seems  likely  to  be  better  than 
the  present.  Hence  a  passion  to  overturn  things  and  take  a 
new  start.  It  is  the  opportunity  of  the  agitator,  for  misery  is 
indefinitely  credulous — hopelessly  thoughtless — never  intellec- 
tual and  analytical.     The  "quadrennial  revolution"  or  "bi- 


SOCIETAL  EVOLUTION  147 

ennlal  revolution,"  as  an  American  election  has  been  called, 
is  a  conflict  of  interests  rather  than  one  of  state-craft:  debtors 
versus  creditors,  ins  versus  outs.  How  can  the  masses  pass 
intelligently  on  an  issue  like  that  of  the  tariff  or  the  gold 
standard,  when  it  takes  a  super-expert  to  understand  them? 
Add  to  this  the  thick-and-thin  adherence  to  party,  the  shufflings 
and  compromises  of  leaders,  the  personal  animosities,  the  cam- 
paign of  emotional  propaganda,  and  what  becomes  of  the 
election  as  an  agency  of  rational  selection  between  proposed 
adjustments  to  the  nation's  life-conditions? 

The  fact  is  that  there  are  a  number  of  phases  of  any  nation's 
code  which  are  beyond  the  pale  even  of  criticism;  reason  is  not 
invited  to  scrutinize  them,  and  if  it  attempts  to  do  so,  it  is 
roughly  bidden  to  desist.  There  are  plenty  of  details  in  any 
code  of  mores  which  we  cling  to  with  as  deep  emotion  as  the 
savage  shows  for  his  medicine-bag,  and  which  it  would  be 
sacrilege  to  submit  to  the  searchlngs  of  reason.  One  cannot 
expect  rational  selection  in  the  field  of  religion,  nor  of  marriage 
and  the  family.  The  Mohammedan  is  not  ready  to  analyze 
the  merits  and  demerits  of  Islam,  and  abide  by  the  results;  nor 
the  monogamist  to  make  a  cold-blooded  study  of  the  merits 
and  demerits  of  pair-marriage.  The  people  love  one  public 
figure,  and  overlook  or  smile  at  his  defects ;  they  hate  another, 
and  jeer  at  or  misrepresent  his  virtues.  Where  feeling  is 
strong,  reason  counts  for  little.  It  is  cynically  said  that  the 
chief  function  of  the  human  mind  is  to  think  up  reasons  for 
doing  what  one  wants  to  do,  or  to  find  good  reasons  for  having 
done  what  one  wanted  to  do. 

These  considerations  may  seem  dismal  to  one  who  would 
like  to  believe  that  men  think  out  society's  destiny;  but  they  do 
not  seem  discouraging  to  one  who  believes  that  the  operation 
of  the  big,  impersonal,  automatically  working  forces  always 
gets  truer  results  than  do  the  feeble  powers  of  the  human 
mind;  that  natural  law  is  far  more  reliable  than  men's  enact- 


148  THE  EVOLUTION  OF  MAN 

ments.  Most  men  would  make  hopeless  errors  In  the  piloting 
of  society.  But  they  are  generally  pretty  clear  as  to  their 
immediate  personal  interests.  If  these  interests  are  in  the 
hands  of  the  interested — if  people  are  minding  their  own 
business — they  are  in  the  custody  of  precisely  those  who  are 
best  capable  of  handling  them.  People  with  common  interests 
make  common  cause  and  form  competing  groups;  and  out  of 
the  competition  of  such  groups  selection  affecting  the  destiny 
of  the  whole  society  is  bound  to  come. 

It  is  bound  also,  in  the  long  run,  to  result  in  adjustment. 
It  is  by  such  automatic,  unplanned  selection  that  all  that  we 
call  improvement  in  adjustment  has  come  to  pass.  The  big 
man  is  the  individual  who  correctly  diagnoses  the  trend  of 
events  and  rides  In  upon  a  wave  of  public  opinion  formed 
under  a  variety  of  motives  which  are  often  totally  irrelevant  to 
the  results  attained.  That  a  wave  of  public  opinion  shall  be 
raised,  It  is  necessary  that  there  shall  exist  a  popular  dis- 
content, or  irritability  that  can  be  excited  to  express  Itself  in 
action,  and,  given  this  condition,  it  is  necessary  to  fit  the  appeal 
to  the  variety  of  interests  involved — interests  which  will  be 
found  to  be  for  the  most  part  personal,  local,  and  but  slightly 
or  not  at  all  relevant  to  any  central  principles.  Masses  of 
men  do  not  look  critically  into  the  rational  merits  of  a  case. 
In  this  country,  for  instance,  it  is  generally  assumed  that  dis- 
comfort is  due  to  governmental  inefficiency  or  worse,  and 
therefore  hard  times  are  likely  to  result  in  the  upset  of  an 
administration.  The  process  by  ex  parte  conviction  and  snap- 
judgment  is  natural  enough,  and  is  shocking  to  those  only  who 
revolt  at  seeing  things  as  they  are. 

It  will  be  a  long  time  before  public  opinion  will  form  itself 
deliberately  upon  thought  In  terms  of  society.  Few  can  en- 
visage so  large  and  complex  a  thing.  The  eugenists  seem  to 
hope  that  people  will  come  to  mate  or  refrain  from  mating 
with  the  interests  of  future  generations  in  mind;  but  only  the 


SOCIETAL  EVOLUTION  149 

very  enlightened  few  can  be  imagined  as  so  doing.  Human 
beings  act  upon  interest  as  they  see  it;  and  interests  are  bound, 
for  the  masses  of  mankind  (who  must  do  the  selecting  that  is 
done),  to  be  narrowly  circumscribed. 

That  this  is  a  counsel  of  despair  is  nothing  against  it,  if  it 
is  true.  But  it  is  not  such  a  counsel.  Societal  evolution  is  a 
vast  process,  where  the  forces  are  massive  and  act  with  un- 
hurried deliberation,  endlessly  interlocking,  within  a  spacious 
field.  There  are  dim  ages  of  the  process  behind  us,  and  ages 
untold  yet  to  come.  Selection  occurs  at  every  stage,  and  is 
but  an  episode  along  the  course. 

How  then  can  men  do  anything,  if  all  Is  determined  by  such 
cosmic  power?  Why  struggle?  Well,  man  can  do  something 
with  gravitation,  with  the  expansive  power  of  steam,  with  the 
germ-plasm  stream,  although  he  can  control  the  processes 
themselves  in  no  degree.  He  can  move  things  about,  into  the 
path  or  out  of  the  path  of  natural  forces.  He  can  fix  the  mill- 
wheel  beneath  the  falling  water.  He  can  place  the  cylinder  in 
the  way  of  the  steam.  He  can  isolate  or  bring  together  the 
sexes  of  animals.  This  has  been  done  so  successfully  for 
man's  interests  and  welfare  that  man  has  conceived  the  idea 
that  he  is  master  of  nature.  But  what  he  has  done  is  to  learn 
nature's  ways  and  adapt  his  action  to  them.  At  a  pinch  he  is 
nature's  plaything  and  victim:  the  earth  shakes  a  little,  and 
his  great  works  collapse;  the  volcano  spills  a  little  gas  over 
its  crater-rim  upon  a  town,  and  the  lords  of  nature  lay  them 
down  and  are  still. 

It  is  not  otherwise  with  the  elemental  forces  of  the  societal 
realm.  They  cannot  be  mastered;  they  must  be  studied  and 
known  and  adjusted  to,  as  a  condition  of  societal  well-being. 
The  efforts  of  many  a  would-be  benefactor  and  upllfter  of  the 
race  are  sterile  or  even  harmful  because  he  is  trying  to  do 
what  he  would  realize,  if  he  knew  what  a  society  is,  and  what 
can  and  cannot  be  done  with  it,  to  be  out  of  the  question. 


I50  THE  EVOLUTION  OF  MAN 

Every  one  knows  that  water  will  not  run  uphill;  yet  in  the 
societal  realm  there  have  been  plenty  of  well-meaning  people, 
through  the  ages,  who  have  worn  out  and  wasted  their  lives 
in  unhappiness,  trying  ineffectually  to  overcome  a  societal 
tendency  and  law  which  are  equally  inevitable.  If  an  ignora- 
mus plays  about  in  a  chemical  laboratory,  we  keep  our  dis- 
tance, for  we  expect  trouble  as  a  result  of  ignorance  of  chemical 
substances  and  laws.  Knowledge  of  the  experimenter's  good 
intentions  or  orthodoxy  does  not  reassure  us  at  all.  But  we 
easily  permit  the  uninformed  meddler  to  prowl  about  the 
structure  of  society,  poking  and  tinkering,  apparently  in  the 
belief  that,  provided  his  intentions  are  good,  nothing  but 
human  weal  can  result.  We  are  bound  to  learn,  sometime, 
that  powerful  forces  are  at  work  within  the  societal  range,  and 
that  ignorant  tampering  is  even  more  dangerous  here  than 
elsewhere  because  so  many  more  people  have  to  endure  the 
consequences.  Then  we  shall  want  more  knowledge  of  these 
forces,  that  we  may  adjust  to  them. 

Intelligent  adjustment  to  the  known  inevitable  is  as  rare 
on  earth  as  automatic  adjustment  to  the  unknown  inevitable 
is  common.  But  the  former  is  an  abridged  and  less  painful 
process.  Adaptation  is  sure,  because  it  is  the  condition  of 
comfort  and  of  life  itself.  Adaptability  is  that  which  hurries 
and  eases  the  process.  Of  all  earthly  things  that  which  pos- 
sesses the  supreme  capacity  for  swift  adaptation  is  the  human 
mind.  But  that  capacity  is  undeveloped,  fettered  in  its  action 
by  pseudo-knowledge,  bias,  caprice,  and  sentimentality — except 
where  tests  and  verification  are  immediate  and  conclusive,  and 
where,  therefore,  knowledge  is  almost  automatically  acquired. 
Nowhere  is  real  knowledge  and  science  so  little  in  intelligent 
demand  as  in  the  societal  realm,  for  the  latter  is  self-sown  to 
whims  and  dreams  of  all  varieties.  It  is  thought  that  man  can 
here  have  his  own  will;  here,  at  last  and  at  least,  he  is  lord. 
He  senses  no  elemental  powers  in  the  field.    Here,  of  all  places, 


SOCIETAL  EVOLUTION  151 

he  needs  but  to  plan  and  "create" ;  pass  resolutions  and  regula- 
tions; think  out  Utopias  in  bed  and  then  rise  and  gird  himself 
to  their  realization ;  abolish  property,  or  the  family,  or  govern- 
ment, or  religion.  Naturally  he  is  taken  by  the  theory  that 
societal  evolution  is  by  individual  purposeful  action.  Naturally 
he  regards  insistence  upon  the  control  exerted  by  spontaneous, 
automatic,  and  impersonal  forces  as  an  assault  upon  his  "free 
will." 

Sometimes,  in  a  crisis,  the  verities  stand  forth  and  enforce 
to  themselves  an  attention  which  they  do  not  get  in  ordinary 
times.  Many  people  have  been  for  some  time  perplexed  and 
in  weak  despair  because  their  comfortable  little  formulas  have 
cracked  and  broken  under  the  weight  of  explanation  laid  upon 
them.  Perhaps  it  is  a  favorable  occasion  to  offer  the  conten- 
tion that  "social  theory"  is  not  wholly  academic  after  all. 


I 


CHAPTER  VI 
THE  TREND  OF  EVOLUTION^ 

EDWIN  GRANT  CONKLIN 

PROFESSOR  OF  BIOLOGY,   PRINCETON    UNIVERSITY 

If  In  the  manner  of  the  Olympian  gods  we  mortals  could 
have  viewed  from  some  exalted  place  the  grandest  drama 
which  has  ever  unfolded  itself  on  this  planet,  namely,  the 
origin  and  evolution  of  life,  and  if  In  the  manner  of  the  modern 
"movie"  we  could  have  seen  this  drama  speeded  up  so  as  to 
bring  the  whole  of  it  within  the  sight  and  experience  of  any 
one  person,  with  what  surprise  should  we  have  watched  the 
marvelous  appearances  and  transformations  which  at  almost 
every  step  have  marked  Its  progress,  and  how  utterly  impos- 
sible it  would  have  been  to  have  predicted  Its  future  course  or 
from  Its  small  and  weak  beginnings  to  have  foreseen  its  mag- 
nificent developments,  its  tragic  failures,  its  stupendous  suc- 
cesses !  What  merely  human  intellect  could  have  foreseen  In 
those  earliest  protoplasmic  particles  *'the  promise  and  potency 
of  all  life,"  the  million  species  of  animals  and  plants,  the 
monsters  of  the  deep,  the  giant  saurians,  the  mighty  beasts, 
and  finally  man?  Who  could  have  predicted  the  marvelous 
adaptations  for  nutrition,  locomotion,  offense  and  defense 
reproduction,  sensation,  and  coordination?  Who  could  have 
foretold  from  the  earliest  reactions  of  this  primeval  proto- 
plasm the  complicated  and  subtle  behavior  of  plants  and  ani- 
mals and  men?    Who  could  have  foreseen  in  these  reactions 

1 A  portion  of  this  chapter  appeared  in  the  Yale  Reineiv  for  July,  1922. 


THE  TREND  OF  EVOLUTION  153 

the  development  of  an  intellect  capable  of  studying  or  appre- 
ciating, even  to  the  extent  of  wondering  at,  this  marvelous 
drama?  Who  could  have  foreseen  in  the  earliest  stages  of 
the  association  and  dependence  of  individuals  the  future  socie- 
ties of  ants  or  bees  or  men?  Indeed,  who  at  any  stage  in  this 
greatest  drama  of  all  time  could  have  predicted  the  next  scene, 
much  less  the  final  ending? 

If  to  human  intellect  every  former  stage  in  this  process 
would  have  been  unpredictable,  what  likelihood  is  there  that 
future  stages  may  be  predicted?  Surely  these  considerations 
should  weigh  heavily  with  anyone  who  attempts  to  forecast 
even  the  next  step  in  evolution  and  they  should  make  it  plain 
that  the  final  outcome  is  almost  as  completely  hidden  from  us 
as  it  was  from  the  original  amoeba. 

But  in  evolution,  as  in  the  succession  of  generations  of  indi- 
viduals, there  have  been  cycles  which  have  repeated  again  and 
again  particular  principles,  problems,  and  solutions,  just  as 
one  theme  may  form  the  groundwork  of  a  great  symphony. 
All  that  has  been  said  of  the  impossibility  of  predicting  the 
course  and  outcome  of  evolution  could  have  been  said  with 
equal  accuracy  of  the  development  of  an  individual.  Who 
that  had  not  before  witnessed  the  process  of  development 
could  possibly  see  in  an  egg  the  promise  and  potency  of  all 
that  will  develop  out  of  it, — the  complicated  body,  the  remark- 
able instincts,  the  emotions,  intelligence,  and  consciousness, — in 
short,  the  personality  of  a  human  being?  But,  owing  to  the 
fact  that  this  process  of  development  repeats  itself  again  and 
again  with  slight  variations,  it  is  possible  to  predict  its  general 
course  and  outcome  though  not  always  its  particular  details. 
And  so  in  the  case  of  evolution  we  find  that  certain  principles 
and  cycles  repeat  themselves  again  and  again  and  they  make 
it  possible  to  foresee  at  least  dimly  and  in  ghostly  outline  the 
mighty  shadows  and  shapes  of  the  future. 

It  is  in  this  spirit  only  and  not  with  the  vain  imagining  that 


154  THE  EVOLUTION  OF  MAN 

any  human  being  can  predict  particular  events  that  depend 
upon  so  many  factors  as  are  involved  in  the  development  of 
an  individual  or  the  evolution  of  a  race,  that  I  venture  to 
direct  your  attention  to  the  trend  of  human  evolution. 

Causes  and  Directions  of  Past  Evolution 

And  first  it  is  necessary  to  consider  the  chief  causes  of  evo- 
lution in  the  past  and  the  most  important  paths  which  it  has 
followed,  for  there  is  no  way  of  looking  into  the  future  except 
by  the  light  of  the  past.  Unfortunately  our  knowledge  of 
the  causes  of  evolution  is  not  very  complete,  but  the  majority 
of  biologists  agree  that  inherited  variations,  or  mutations, 
constitute  the  building  materials  of  evolution,  while  natural 
selection,  or  the  elimination  of  the  unfit,  is  the  workman  or 
architect  that  selects  or  rejects  these  materials. 

Inheritance  and  Variation.  In  order  to  be  of  any  evolution- 
ary value  a  variation  must  be  inherited.  Thousands  of  varia- 
tions occur  in  organisms  which  are  not  inherited;  they  come 
with  changes  in  food,  climate,  use  or  disuse  or  other  conditions 
of  environment  and  when  these  conditions  change  they  disap- 
pear. These  environmental  variations  are  known  as  ^'fluctua- 
tions";  they  represent  changes  in  development  rather  than  in 
heredity,  modifications  of  the  developed  organism  rather  than 
of  the  germ-plasm.  On  the  other  hand,  inherited  variations 
are  caused  by  changes  in  the  germ-plasm  itself.  These  changes 
may  be  of  two  kinds,  ( i )  those  which  are  due  to  new  com- 
binations or  recombinations  of  old  inheritance  factors,  or  what 
is  known  as  "Mendelism,"  and  (2)  those  which  are  caused  by 
sudden  alterations  in  the  individual  factors  or  genes,  such 
transformations  being  known  as  "mutations." 

Formerly  these  three  types  of  variation,  namely,  fluctuations, 
Mendelian  combinations,  and  mutations,  were  not  clearly  dis- 
tinguished, and  Darwin  assumed  that  all  kinds  of  variation 


I 


THE  TREND  OF  EVOLUTION  155 

might  be  of  evolutionary  value.  We  now  know  that  fluctua- 
tions have  no  evolutionary  value;  Mendelian  combinations 
probably  play  a  secondary  part  in  supplying  the  materials  of 
evolution,  though  this  part  is  not  negligible ;  mutations,  on  the 
other  hand,  are  the  fundamental  and  initial  steps  in  evolution. 
Fluctuations  and  new  Mendelian  combinations  occur  in  count- 
less numbers ;  indeed,  they  may  be  said  to  be  universally  present 
among  organisms;  mutations,  on  the  contrary,  are  relatively 
rare.  Nevertheless,  they  are  by  no  means  uncommon;  during 
the  past  dozen  years  Professor  T.  H.  Morgan  and  his  asso- 
ciates have  found  and  studied  about  four  hundred  mutations 
in  the  pomace  fly,  Drosophila;  few  of  these  were  beneficial 
changes  and  almost  all  of  them  would  have  disappeared  in  a 
state  of  nature,  but  this  probably  indicates  that  natural  species 
and  varieties  are  the  products  of  very  severe  selection,  that 
thousands  of  mutations  have  been  eliminated  where  one  or  a 
few  survive.  Many  of  our  numerous  breeds  of  domestic  ani- 
mals and  cultivated  plants  have  appeared  as  mutations,  and 
while  we  cannot  assume  that  all  that  have  been  preserved  are 
intrinsically  useful  nor  that  all  useful  mutations  have  been  pre- 
served, the  great  number  of  breeds  that  have  arisen  among 
domestic  animals  and  cultivated  plants  indicates  that  useful 
mutations  occur  in  suflicient  numbers  to  furnish  the  materials 
for  evolution. 

There  can  be  no  question  that  the  same  fundamental  prin- 
ciples are  involved  in  the  evolution  of  man  as  in  the  evolution 
of  any  other  organism.  Inheritance  and  variation,  fluctua- 
tions, Mendelian  combinations,  and  mutations  occur  in  the 
human  race,  just  as  in  plants  and  animals.  Furthermore,  there 
is  good  evidence  that  this  is  true  not  merely  of  the  body  but 
also  of  the  mind  and  society  of  man.  The  fundamental  prin- 
ciples in  all  kinds  of  evolution  are  similar  and  if  mutations  and 
new  Mendelian  combinations,  but  not  fluctuations,  are  the  ma- 
terials  of   physical   evolution,    and  natural   selection   is   the 


156  THE  EVOLUTION  OF  MAN 

builder,  it  is  altogether  probable  that  the  same  is  true  of  intel- 
lectual and  social  evolution. 

Mutations  and  Their  Causes.  Regarding  the  causes  of  mu- 
tations we  know  very  little,  but  it  seems  logically  necessary  to 
assume  that  these  causes  are  both  intrinsic  in  the  germ-plasm 
and  extrinsic  in  the  environment;  or,  in  the  language  of  Dar- 
win, "Although  every  variation  is  either  directly  or  indirectly 
caused  by  some  change  in  the  surrounding  conditions,  we  must 
never  forget  that  the  nature  of  the  organization  acted  upon 
essentially  governs  the  results."  The  same  outer  conditions 
acting  upon  different  species  or  individuals  produce  different 
results  and  the  possibilities  of  evolution  are  always  limited  by 
the  organization  of  the  germ-plasm.  Some  conceivable  muta- 
tions do  not  and  cannot  appear  because  of  these  limitations. 
"Whales  never  produce  feathers,  nor  birds  whalebone,"  said 
Huxley;  and  probably  no  one  ever  really  saw  a  green  horse  or 
a  purple  cow.  But,  although  mutations  cannot  take  place  in 
all  conceivable  directions,  there  is  no  justification,  in  recent 
experimental  work,  for  extreme  views  of  orthogenesis  which 
regard  mutations  as  taking  place  in  only  a  single  direction. 
Furthermore,  an  extensive  study  of  mutations  shows  that  they 
are  as  frequently  injurious  as  beneficial;  indeed  they  are  rarely 
as  well  fitted  for  existence  as  the  stock  from  which  they  come. 

It  is  highly  probable  that  mutations  take  place  in  response 
to  changes  in  environment,  but  it  is  necessary  to  remember 
that  the  environment  of  the  germ-plasm  is  not  merely  the  outer 
world  but  also  the  inner  environment  of  the  body  organs  and 
fluids  and  cells,  and  the  innermost  environment  of  the  cyto- 
plasmic and  nuclear  substances  which  surround  the  inheritance 
factors  or  genes. 

Inheritance  of  Acquired  Characters.  But  in  spite  of  the  fact 
that  mutations  probably  occur  in  response  to  changes  in  the 
inner  or  outer  environment,  it  is  practically  certain  that  modi- 
fications or  fluctuations  of  developed  organisms  are  not  trans- 


THE  TREND  OF  EVOLUTION  157 

mitted  to  the  germ  cells  so  as  to  reappear  in  the  next  genera- 
tion. In  short,  there  is  no  inheritance  of  specific  characters 
acquired  by  the  soma.  Evolutionary  changes  do  not  first 
occur  in  developed  organisms  and  then  by  some  mysterious 
process  get  into  the  germ-plasm,  but  evolution  consists  in  an 
evolution  of  germ-plasm  which  then  manifests  itself  in  the 
developed  organism. 

It  is  known  as  a  matter  of  fact  that  acquired  somatic  char- 
acters are  not  usually,  if  ever,  inherited.  Environment,  train- 
ing, education,  may  greatly  modify  glands,  muscles,  nerves,  and 
brains,  but  they  do  not  change  the  germ-plasm  so  as  to  produce 
these  identical  modifications  in  the  next  generation.  In  a  few 
instances  it  seems  probable  that  chemical  substances  in  the 
bodies  of  parents,  such  as  hormones,  or  anti-bodies,  may  in- 
fluence the  germ  cells  or  developing  embryos  so  as  to  produce 
bodily  changes  in  offspring  similar  to  those  in  the  parents,  but 
in  general  it  may  be  said  that  there  is  no  satisfactory  evidence 
that  the  specific  modifications  of  development,  due  to  particular 
conditions  of  life,  enter  into  the  germ-plasm  and  appear  again 
in  the  next  generation,  in  the  absence  of  the  environment  which 
first  called  them  forth.  In  short,  the  effects  on  development 
of  environment,  training,  and  education  are  not  inherited 
through  the  germ  cells  and  the  hope  of  permanently  improving 
the  human  race,  or  any  other  species,  in  this  manner  can  only 
lead  to  disappointment  and  failure. 

Social  Inheritance.  At  the  same  time  it  must  be  remem- 
bered that  man  transmits  to  his  descendants  not  only  a  par- 
ticular germ-plasm  which  determines  bodily  qualities  and  men- 
tal capacities,  but  he  also  hands  down  through  language,  edu- 
cation, and  customs,  his  own  acquirements,  experiences,  and 
possessions  as  well  as  those  of  former  generations.  This  has 
been  called  "social  inheritance"  to  distinguish  it  from  "ger- 
minal inheritance";  it  is  inheritance  in  the  legal  rather  than  in 
the  biological  sense.    In  this  sense  we  have  inherited  from  our 


158  THE  EVOLUTION  OF  MAN 

ancestors  language,  literature,  science,  property,  customs,  in- 
stitutions. These  are  no  part  of  our  germ-plasm,  nor  even 
of  our  blood  and  brain,  but  rather  of  our  environment.  Be- 
cause of  this  social  inheritance  society  may  advance  from  age 
to  age,  each  generation  starting  where  the  preceding  one 
ended,  as  in  a  relay  race, — whereas  in  our  germinal  inherit- 
ance each  generation  begins  where  the  previous  one  began, 
namely  from  an  egg  cell,  and  the  whole  course  of  development 
must  be  repeated  in  each  generation.  Civilization  is  the  re- 
sult of  the  accumulations  of  social  inheritance,  and  the  future 
progress  of  society  must  depend  largely  upon  this  capacity  of 
profiting  by  the  experiences  of  former  generations. 

Natural  Selection.  If  mutations  are  the  materials,  natural 
selection  is  the  architect  and  director  of  evolution,  for  although 
it  does  not  originate  fitness  it  continually  eliminates  the  unfit 
and  in  the  long  run  preserves  only  the  fit.  In  certain  quarters 
it  has  been  fashionable  of  late  to  decry  the  importance  of 
natural  selection,  but  more  and  more,  biologists  are  coming 
to  recognize  that  it  is  the  most  important  directing  and  per- 
fecting factor  in  evolution. 

Natural  selection  in  its  widest  meaning  involves  not  merely 
the  overproduction  of  individuals  and  the  consequent  struggle 
for  existence  with  elimination  of  the  unfit,  as  Darwin  formu- 
lated it,  but  it  also  includes  the  overproduction  of  many  vital 
activities,  such  as  motions  and  reactions,  with  the  elimination 
of  the  unfit,  as  in  the  process  known  as  "trial  and  error." 
Thus  useful  behavior  is  the  residue  left  after  useless  responses 
are  eliminated,  and  it  is  not  necessary  to  hold  with  Darwin 
that  fitness  is  always  the  result  of  the  elimination  of  unfit 
persons.  It  is  often  the  result  of  the  elimination  of  unfit  re- 
actions. In  short,  natural  selection  is  not  only  personal  but 
also  intra-personal. 

Furthermore  there  are  many  kinds  of  fitness  not  only  for 
different  environments  but  also  for  different  organisms  and 


THE  TREND  OF  EVOLUTION  159 

lines  of  evolution.  Physical,  intellectual,  and  social  fitness  are 
very  different  things,  and  it  is  possible  to  have  any  one  of 
these  without  the  other  two.  The  past  evolution  of  the  human 
race  has  been  guided  by  the  elimination  of  the  unfit,  whether 
physical,  intellectual,  or  social,  and  the  future  progress  of  the 
race  must  depend  on  this  same  process. 

The  Paths  of  Progress.  Even  a  cursory  study  of  the  living 
world  would  justify  the  opinion  that  evolution  has  proceeded 
in  all  possible  directions;  crab-like  it  moves  forward,  back- 
ward, and  sidewise.  This  is  especially  true  of  the  minor 
stages  of  evolution  represented  by  mutations,  for  these  ap- 
parently occur  in  all  directions  without  reference  to  their  utility 
or  inutility;  however,  in  order  to  survive  and  become  estab- 
lished, a  mutation  must  run  the  gauntlet  of  natural  selection 
and  injurious  mutations  are  eliminated.  Much  more  is  this 
true  of  species  and  larger  groups  which  have  had  a  longer  and 
more  severe  trial  than  mutations  and  are  consequently 
peculiarly  adapted  to  their  environments.  In  particular  in- 
stances simplification  and  degeneration  have  occurred  but  in 
the  main  evolution  has  been  progressive,  that  is,  it  is  marked 
by  increasing  complexity  of  structures,  functions,  and  adapta- 
tions, just  as  development  from  the  egg  to  the  adult  is  gener- 
ally progressive,  though  in  some  instances  and  stages  it  is 
retrogressive.  Particularly  when  one  surveys  the  whole  course 
of  phylogeny  or  ontogeny  it  is  evident  that  there  has  been 
progress  from  relative  simplicity  to  complexity. 

Definition  of  Progress.  The  very  word  "progress"  calls 
forth  a  reaction  from  some  people  not  unlike  their  response 
during  the  war  to  the  word  Kiiltur.  A  few  persons  seem 
to  deny  the  existence  of  any  such  thing  as  progress,  while  others 
insist  that  it  is  too  indefinite  to  admit  of  any  formulation. 
Undoubtedly  progress  may  occur  in  many  different  directions 
and  toward  different  goals,  but  everywhere  and  always  in  the 
living  world,  it  has  certain  fundamental  characteristics.    As  is 


i6o  THE  EVOLUTION  OF  MAN 

generally  true  in  complex  phenomena  It  is  best  defined  in  terms 
of  causes  rather  than  of  results. 

Everywhere  in  the  living  world,  progress  is  brought  about 
by  increasing  specialization  and  cooperation,  or,  in  the  lan- 
guage of  biology,  by  increasing  differentiation  and  integration. 
Whether  it  be  the  development  of  an  egg  into  an  adult,  the 
evolution  of  primitive  animals  and  plants  into  their  more  com- 
plex descendants,  or  the  development  and  evolution  of  the 
body,  mind,  and  society  of  man,  progress  everywhere  is  caused 
by  increasing  specialization  and  cooperation.  In  the  develop- 
ment of  an  egg,  which  is  the  symbol  and  epitome  of  all  prog- 
ress, there  is  segregation  of  different  structures  and  functions 
in  different  cells  and  parts  of  the  body,  that  is,  there  is  mor- 
phological division  of  substance  and  physiological  division  of 
labor,  and  at  the  same  time  there  is  increasing  perfection  of 
functions  and  adaptations.  In  the  evolution  of  limbs  or  eyes 
or  brains  there  is  a  similar  increase  in  the  complexity  of  differ- 
entiation and  integration.  In  both  the  ontogenetic  and  the 
phylogenetic  development  of  intellect  and  of  society,  there  is 
increasing  complexity  and  perfection  of  function  and  adapta- 
tion. All  kinds  of  progress,  whether  of  body,  mind,  society, 
art,  industry,  or  science,  are  marked  by  increasing  specializa- 
tion and  cooperation.  As  thus  defined,  progress  may  lead  in 
different  directions  to  very  different  ends,  as  is  shown  in  the 
various  types  of  locomotion,  offense  and  defense,  sense  organs, 
nervous  systems,  etc.,  found  in  the  animal  kingdom.  In  man  it 
has  led  to  increased  cranial  and  intellectual  capacity,  increased 
control  over  environment  and  greater  freedom,  increased  size 
and  complexity  of  social  units,  etc.  But  progress  in  each  of 
these  many  paths  is  caused  by  increasing  complexity  and  per- 
fection of  specialization  and  cooperation. 

Limits  of  Progress.  Biological  progress,  however,  always 
has  its  limits;  sooner  or  later  differentiation  reaches  a  stage 
beyond  which  it  cannot  go  without  destroying  the  internal 


THE  TREND  OF  EVOLUTION  i6i 

balance,  or  integration,  and  the  adaptability  to  external  condi- 
tions. Furthermore,  in  the  higher  types  of  organization  the 
mutual  dependence  of  parts  becomes  so  great  that  when  one 
of  these  is  injured  or  breaks  down  it  carries  with  it  to  destruc- 
tion the  entire  organism.  As  Professor  Minot  used  to  say, 
''Death  is  the  price  we  pay  for  our  differentiation."  Germ 
cells  and  embryonic  cells  are  potentially  immortal,  but  tissue 
cells  are  not  self-sustaining  and  the  more  highly  they  are  dif- 
ferentiated the  greater  is  their  dependence  and  the  more 
certain  is  their  ultimate  death. 

The  record  of  the  rocks  is  full  of  instances  in  which  groups 
of  organisms  have  progressed  to  greater  and  greater  com- 
plexity and  have  then  become  extinct.  The  roads  of  progress 
are  strewn  with  the  remains  of  creatures  fearfully  and  won- 
derfully specialized,  but  which  were  unable  to  preserve  inter- 
nal balance  or  to  adapt  themselves  to  new  environments  and 
which  therefore  perished.  Indeed,  in  practically  every  instance 
the  road  of  ever  increasing  progress  ends  in  extinction.  But 
just  as  in  the  succession  of  generations  highly  differentiated 
cells  and  individuals  die  and  new  generations  arise  from  rela- 
tively undifferentiated  eggs,  so  when  highly  differentiated 
species  become  extinct  new  lines  of  progress  start  from  gen- 
eralized rather  than  from  highly  specialized  types. 

It  is  of  course  conceivable  that  differentiation  might  go  on 
indefinitely  in  any  line,  the  elephant  might  get  a  longer  trunk, 
the  giraffe  a  longer  neck,  and  man  a  larger  and  larger  brain, 
but  while  such  things  are  conceivable  they  are  not  practicable 
for  the  reasons  named.  In  any  line  of  evolution  progress  is 
most  rapid  at  first  and  then  it  gradually  slows  down  until  it 
stops,  and  in  every  well-tried  path  of  evolution,  progress  has 
practically  come  to  an  end;  further  progress,  if  it  occurs,  must 
be  in  new  lines  and  from  relatively  undifferentiated  stock. 

Progressive  Evolution  of  Man.  There  have  been  three 
main  lines  of  human  evolution, — physical,  intellectual,  social, — 


1 62  THE  EVOLUTION  OF  MAN 

and  it  is  generally  assumed  that  in  each  of  these  lines  we  may 
look  forward  to  endless  progress.  The  infinite  perfectability 
of  man  is  a  fundamental  article  of  faith  with  many  people, 
and  yet  all  biological  evidence  indicates  that  it  is  not  supported 
by  fact.  Not  only  the  history  of  other  organisms  but  also  that 
of  man  himself  indicates  that  progress  in  any  particular  line 
is  limited. 

In  bodily  evolution  man  has  made  no  very  marked  progress 
during  the  last  twenty  thousand  years  at  least.  Undoubtedly 
there  have  been  minor  changes  in  the  human  body,  probably  an 
increasing  resistance  to  certain  diseases  due  to  the  elimination 
of  those  persons  who  were  more  susceptible,  as  well  as  certain 
degenerative  changes  in  sense  organs,  hair,  teeth,  and  toes; 
but  such  changes  are  insignificant  when  compared  with  those 
which  marked  the  transition  from  pre-human  ancestors  to  man, 
or  even  those  changes  which  brought  about  the  differentiation 
of  the  primary  races  of  mankind.  The  physical  evolution  of 
man  has  slowed  down  almost  to  a' standstill,  and  if  it  is  to  go 
forward  again  it  will  probably  be  in  new  lines  and  in  response 
to  new  and  very  different  environmental  conditions. 

The  opinion  is  widely  held  that  intellectual  evolution  is 
advancing  rapidly  and  in  justification  of  this  belief  is  instanced 
our  increasing  knowledge  of  the  world  and  of  man.  But  it 
is  necessary  to  distinguish  between  intellect  and  knowledge, 
between  the  capacity  for  knowing  and  things  known.  Un- 
doubtedly we  know  many  more  things  than  the  ancients  or 
even  than  our  own  parents,  but  has  there  been  any  increase  in 
intellect  comparable  with  the  increase  in  knowledge  which  has 
marked  the  last  few  centuries?  On  the  contrary,  those  who 
have  devoted  much  attention  to  this  subject  are  of  the  opinion 
that  no  modern  race  is  intellectually  equal  to  the  ancient  Greek 
race.  Not  only  did  this  race  produce  a  larger  number  of  illus- 
trious men  than  has  any  other  race  during  an  equal  period  of 


THE  TREND  OF  EVOLUTION  163 

time  but  the  general  intelligence  of  the  citizens  was  probably 
higher  than  in  any  modern  nation. 

Undoubtedly  popular  education  brings  to  light  many  per- 
sons of  marked  intellectual  capacity  who  in  former  years  might 
have  remained  "mute,  inglorious  Miltons";  there  are  many 
more  opportunities  to-day  for  discovering  the  inherited  capaci- 
ties of  men  than  there  were  in  ancient  times,  but  anyone  who 
thinks  that  intellectual  capacity  is  undergoing  rapid  evolution 
needs  to  consider  seriously  the  widespread  emotionalism,  irra- 
tionalism,  and  superstition  of  this  twentieth  century  of  en- 
lightenment as  compared  with  the  golden  age  of  Greece  in  the 
fourth  or  fifth  century  B.  c.  Indeed,  since  the  times  of  the 
Cro-Magnon  race,  probably  twenty  thousand  years  ago,  there 
has  been  no  marked  increase  in  man's  cranial  capacity,  and 
probably  little  or  no  increase  in  his  inherent  intellectual  ability. 
There  are  better  opportunities  to-day  than  ever  before  for  the 
development  of  the  individual  but  the  intellectual  evolution 
of  the  race,  no  less  than  the  physical,  has  slowed  down  until  it 
has  practically  stopped. 

In  human  society,  however,  tremendous  changes  are  taking 
place  and  many  of  these  are  in  the  direction  of  progress.  The 
great  advances  in  our  knowledge  of  and  control  over  nature, 
which  are  such  a  distinctive  feature  of  our  present  civiUzation, 
are  the  results  of  cooperative  effort.  The  developments  of 
science,  literature,  and  art,  of  agriculture,  industry,  and  com- 
merce, of  education,  government,  and  religion,  are  the  products 
of  increased  specialization  and  cooperation  of  society.  The 
fact  that  social  change  is  going  on  so  much  more  rapidly  than 
either  physical  or  mental  evolution  is  due  to  the  fact  that  past 
experiences  and  acquired  characters  are  handed  down  through 
"social  inheritance,"  but  not  through  the  germ-plasm.  If  we 
consider  those  social  changes  only  which  are  due  to  modifica- 
tions of  the  germ-plasm,  such  as  inherited  instincts  and  capaci- 
ties, we  find  that  evolution   is  probably  no  more  rapid  in 


1 64  THE  EVOLUTION  OF  MAN 

society  than  in  the  case  of  the  body  or  mind  of  man.    Within 

historic  times  the  social  instincts  of  men  have  not  changed 

more  fundamentally  than  their  intellectual  capacities  or  their 

germ-plasm. 

Unlike  any  other  form  of  evolution,  the  rapid  changes  which 
are  taking  place  in  human  society  are  not  due  to  changes  in 
germ-plasm,  nor  even  to  changes  in  the  developed  individual, 
but  merely  to  changes  in  environment.  They  are  not  even 
skin-deep,  they  are  only  clothes-deep.  It  may  be  questioned 
whether  these  changes  are  really  evolutionary  at  all  since  they 
do  not  involve  changes  in  germinal  inheritance,  intellectual 
capacity,  or  social  instincts,  but  are  merely  the  accumulation  of 
experiences  from  generation  to  generation,  as  an  individual 
accumulates  knowledge  from  year  to  year.  Indeed,  the  prog- 
ress of  human  society  is  much  more  like  the  development  of 
an  individual  than  it  is  like  the  evolution  of  a  species. 

But  whether  we  regard  social  development  as  a  form  of 
phylogeny  or  of  ontogeny,  as  a  result  of  inheritance  or  of 
environment,  we  cannot  fail  to  see  that  it  is  going  forward  at 
a  rapid  rate  and  that  it  is  fraught  with  the  most  stupendous 
possibilities  for  the  future.  The  only  great  progress  which 
the  human  race  has  made  during  the  past  twenty  thousand 
years  has  been  social,  and  so  far  as  we  can  now  see  into  the 
future  the  progressive  evolution  of  mankind  must  depend  to 
a  great  extent  upon  society.  It  is  particularly  in  the  field  of 
discovery  and  invention  that  progress  has  been  most  notable. 
Nothing  could  more  strikingly  illustrate  this  than  the  compari- 
son of  the  state  of  the  world  one  hundred  years  ago  with  that 
of  to-day.  Whole  regions  of  the  universe  have  been  explored, 
the  very  existence  of  which  was  not  dreamed  of  a  generation 
ago.  Inventions  which  would  seem  incredible  or  magical  were 
they  not  so  common  are  everyday  conveniences.  Diseases  and 
epidemics  which  were  once  regarded  as  the  direct  acts  of  an 
inscrutable  Providence  or  of  unscrupulous  demons  are  now 


THE  TREND  OF  EVOLUTION  165 

prevented  or  controlled.  All  this  notable  progress  in  the  con- 
quest of  nature  is  the  result  of  cooperative  effort.  No  one 
person,  however  great  his  contributions,  could  have  made  any 
important  advance  alone  and  unaided.  Every  discovery  is 
based  upon  many  others  which  have  gone  before,  and  all  civi- 
lized countries  and  ages  have  contributed  to  the  advancement 
of  knowledge.  In  short,  progress  during  historic  times  has 
not  been  in  the  individual  but  in  the  association  of  individuals, 
not  in  the  inherited  capacities  of  persons  but  in  the  organiza- 
tion of  society. 

Not  only  the  direction  of  social  evolution,  but  also  the  future 
evolution  of  the  body  and  mind  of  man  will  be  determined  to 
a  great  extent  by  society.  Progress  through  natural  selection 
is  exceedingly  slow  and  wasteful,  intelligence  is  a  great  time- 
saver  as  contrasted  with  ''trial  and  error,"  and  intelligent  arti- 
ficial selection  affords  the  most  rapid  and  satisfactory  means 
for  the  improvement  of  the  human  race.  There  is  no  doubt 
that  mankind  could,  if  it  would,  breed  a  more  healthy,  more 
intelligent,  more  moral  type  than  the  general  average  of  the 
existing  race.  By  means  of  artificial  selection,  requiring  no 
more  intelligence  than  that  which  is  now  used  in  the  breeding 
of  domestic  animals,  weakness  of  body,  of  mind,  and  of  social 
instincts  could  be  largely  eliminated,  and  the  average  of  the 
race  could  be  raised  to  a  level  more  nearly  that  of  the  best 
existing  individuals.  To  a  large  extent  mankind  will  deter- 
mine its  own  destiny  on  this  planet.  Whether  it  has  wit  enough 
to  save  itself  from  the  dangers  which  now  threaten  is  a  serious 
question. 

Present  Conditions  and  Tendencies 

Our  watchers  on  Olympus  would  see  in  present  conditions 
and  tendencies  of  the  human  race  some  promising  prospects 
but  much  cause  for  grave  concern.  Perhaps  the  conditions 
which  would  cause  most  anxiety  are  the  nullification  or  com- 


1 66  THE  EVOLUTION  OF  MAN 

plete  reversal  by  man  of  some  of  the  most  important  principles 
which  have  guided  evolution  in  the  past.  For  the  first  time  in 
the  history  of  life  upon  the  earth,  a  single  species  now  has  the 
power  of  controlling  to  a  large  extent  its  own  evolution,  and 
it  has  begun  by  radically  changing  some  of  the  conditions  of 
progress  which  have  prevailed  hitherto.  A  large  part  of  the 
human  race  is  now  engaged  in  the  most  stupendous  and  dan- 
gerous experimentation  upon  itself;  without  any  adequate 
knowledge  of  the  mechanism  of  evolution  it  has  begun  to  tinker 
with  that  mechanism,  throwing  certain  parts  out  of  gear,  de- 
stroying others,  and  in  general  paying  little  or  no  attention  to 
the  results. 

Decreasing  Influence  of  Natural  Selection.  In  spite  of  some 
notable  exceptions,  the  leading  biologists  of  the  world  agree 
that  natural  selection  has  been  the  most  important  guiding 
and  perfecting  principle  in  past  evolution,  and  on  the  whole 
it  has  made  for  progress.  At  every  step  in  the  past  course  of 
evolution  it  has  sifted  the  unfit  from  the  fit,  and  while  it  has 
not  originated  fitness,  It  has  preserved  it,  and  in  general  it  has 
directed  evolution  Into  paths  of  progress  by  closing  up  other 
paths.  Those  whose  only  conception  of  natural  selection  is 
that  of  a  Hfe  and  death  struggle  between  individuals  of  the 
same  species  may  well  rejoice  that  mankind  Is  to  a  certain 
extent  freed  from  this  struggle,  and  that  In  human  society 
cooperation  Is  becoming  a  more  Important  means  of  progress 
than  competition.  But  natural  selection  in  its  widest  sense 
means  the  elimination  of  the  unfit,  whether  these  are  reactions, 
Instincts,  customs,  persons,  races,  or  species;  and  if  In  human 
society  cooperation  Is  more  beneficial  than  competition,  co- 
operation rather  than  competition  will  be  favored  by  natural 
selection.  And  In  similar  manner  if  intelligence  Is  more  bene- 
ficial than  brute  strength  or  cunning  or  instinct.  Intelligence 
will  be  favored.  In  short,  there  are  many  kinds  of  fitness  in 
different  lines,  and  In  the  case  of  man,  if  natural  selection  were 


THE  TREND  OF  EVOLUTION  167 

not  interfered  with,  it  would  lead  to  the  partial  or  complete 
elimination  not  only  of  the  physically  unfit  but  also  of  those 
who  are  mentally  and  socially  unfit. 

Of  course  man  cannot  wholly  eradicate  natural  selection 
from  human  life ;  the  most  monstrous  forms  cannot  possibly  be 
saved  and  the  more  abnormal  they  are  the  earlier  they  die;  the 
seriously  defective  rarely  come  to  maturity  or  are  capable  of 
reproduction  and  even  those  that  survive  and  reproduce  are 
usually  handicapped  at  every  stage.  Natural  selection  remains 
and  will  probably  ever  remain  an  important  factor  in  human 
evolution,  but  just  as  far  as  is  possible  it  is  being  minimized 
or  set  aside  in  civilized  states.  In  the  finest  fervor  of  altruism 
and  with  the  most  extraordinary  expenditure  of  money  and 
effort  civilized  society  manages  to  save  many  of  those  who 
are  feeble  in  mind  and  body  as  well  as  criminals  and  enemies 
of  society.  And  no  doubt  much  of  good  is  gained  in  this  way, 
for  not  only  are  great  minds  and  souls  sometimes  lodged  in 
frail  bodies  but  it  is  probably  more  valuable  to  the  race  to  pre- 
serve a  spirit  of  altruism  and  social  justice  than  it  is  to  rid 
society  of  its  degenerates  by  ruthless  methods.  Nevertheless, 
neither  justice  nor  altruism  requires  that  such  persons  be  per- 
mitted to  propagate  their  kind;  lasting  progress  cannot  be 
based  upon  a  one-sided  development  of  body  or  mind;  ideally, 
as  well  as  biologically,  life  and  progress  are  balanced  as  it 
were  between  many  different  forces,  principles,  and  ends,  and 
neither  physical,  intellectual,  nor  social  developments  should 
go  so  far  as  to  destroy  either  of  the  others. 

Galton  says,  ''Our  human  stock  is  far  more  weakly  through 
congenital  imperfection  than  that  of  any  other  species  of 
animals,  whether  wild  or  domestic."  It  cannot  be  doubted  that 
this  greater  weakness  and  imperfection  is  due  to  failure  to 
eliminate  the  unfit,  but  there  is  no  clear  evidence  as  to  whether 
congenital  physical  degeneracy  is  increasing  or  decreasing  at 
the  present  time.    Athletics,  physical  education,  medicine,  and 


1 68  THE  EVOLUTION  OF  MAN 

sanitation  have  made  great  advances  in  recent  years  and  this 
has  had  a  beneficial  influence  on  the  health  and  vigor  of  this 
generation,  but  there  is  no  satisfactory  evidence  that  these 
effects  are  inherited.  The  average  length  of  life  has  been 
increased,  chiefly  by  saving  the  babies,  but  the  maximum  length 
of  Hfe  has  not  been  raised;  men  live  no  longer  now  than  in 
the  time  of  Methuselah,  and  since  longevity  is  hereditary,  it 
may  well  be  that  the  artificial  prolongation  of  the  lives  of  those 
who  are  hereditarily  weak  and  short-lived  may  actually  reduce 
the  natural  longevity  of  the  race  as  a  whole. 

Mental  and  moral  degeneracy  runs  in  families,  as  is  proved 
by  such  cases  as  the  "Jukes,"  "Kalikaks,"  "Zeros,"  "Nams," 
"Ishmaels,"  etc.,  but  social  selection  against  such  groups  is 
pretty  severe  and  it  does  not  seem  probable  that  extreme  de- 
fectives of  this  class  are  increasing  very  rapidly.  Inmates  of 
custodial  institutions  are  usually  prevented  from  having  off- 
spring and  they  do  not  greatly  threaten  racial  standards;  the 
greatest  danger  comes  from  somewhat  less  defective  indi- 
viduals who  are  at  large  and  are  free  to  have  as  many  children 
as  they  can. 

Retrogressive  Selection  of  Civilization.  Much  worse  than 
this  partial  failure  of  natural  selection  is  the  retrogressive 
selection  of  civilization.  If  society  had  deliberately  set  about 
the  propagation  of  the  unfit  it  could  hardly  have  devised 
more  effective  means  than  many  of  those  which  are  now  in 
vogue.  Frequent  wars  have  taken  the  best  blood  of.  the  na- 
tions, and  while  casualties  In  modern  battle  are  more  or  less 
indiscriminate,  soldiers  represent  a  selected  group;  those  who 
go  to  war  are  usually  the  young,  the  strong,  the  capable,  while 
the  weak.  Incompetent,  and  degenerate  are  left  behind  as  unfit 
for  military  service.  Furthermore,  these  casualties  must  be 
doubled  when  their  Influence  on  the  race  Is  considered,  for  In 
general  every  man  killed  leaves  one  woman  unmated  for  life. 
As  a  result  of  the  last  war  millions  of  women  can  never  marry 


THE  TREND  OF  EVOLUTION  169 

or  have  children.  Among  these  are  some  of  the  best  human 
stock  the  world  possesses, — and  thus  the  race  is  made  poorer 
for  many  generations  to  come.  Enforced  celibacy  in  many 
religious  orders  and  societies  of  scholars  has  led  to  the  ex- 
tinction of  some  of  the  world's  most  gifted  lines.  The  present 
customs  of  mate  selection  condemn  many  of  the  finest  women 
in  the  world  to  spinsterhood,  while  the  feather-brained  and 
sexually-daring  "flappers"  readily  find  mates.  On  the  other 
hand,  personal  ambition  and  selfishness,  the  prevalence  of 
prostitution  and  illicit  sexual  relations,  the  fear  of  misalliances, 
divorce,  and  alimony  are  potent  causes  of  bachelorhood.  In 
both  cases  the  results  are  that  many  of  the  best  human  lines 
are  wiped  out.  Galton  has  shown  that  on  the  average  people 
who  marry  at  twenty-two  will  leave  twice  as  many  descendants 
at  the  end  of  a  century  as  those  who  marry  at  thirty-three  and 
in  a  few  generations  they  will  actually  possess  the  earth.  And 
yet  the  increasing  time  required  for  education,  as  well  as  more 
luxurious  standards  of  living,  have  made  early  marriages 
almost  impossible  among  professional  and  business  classes, 
with  whom  the  most  vigorous  and  fertile  years  of  the  repro- 
ductive period  are  years  of  sterility.  Finally,  luxury,  soft 
living,  and  selfishness  have  made  children  unwelcome  among 
many  married  people  who  have  shown  qualities  of  success  in 
life  and  whose  hereditary  traits  are  above  the  average.  Under 
such  conditions  the  general  average  of  intelligence  and  social 
fitness  in  the  race  as  a  whole  must  inevitably  decline. 

There  is  an  evident  tendency  to  assortative  mating  in 
modern  society  due  not  merely  to  similarity  of  social  status 
and  ideals  but  also  to  the  more  potent  factor  of  propinquity. 
Generally  men  and  women  representing  the  extremes  of  the 
social  or  intellectual  scale  do  not  marry  and  it  has  been  claimed 
that  owing  to  this  fact  there  is  a  constant  tendency  for  society 
to  be  split  up  into  hereditary  classes.  Some  authors  maintain 
that  the  more  intelligent  and  the  less  intelligent  elements  of 


I70  THE  EVOLUTION  OF  MAN 

society  are  separating  more  and  more  widely,  that  the  success- 
ful are  being  split  off  from  the  unsuccessful,  and  that,  in  gen- 
eral, human  society  Is  differentiating  Into  hereditary  classes 
owing  to  the  tendency  of  like  to  mate  with  like.  However, 
when  one  considers  the  world  as  a  whole,  rather  than  a  few 
small  social  groups.  It  Is  plain  that  any  such  tendency  to  form 
hereditary  classes  is  more  than  overbalanced  by  other  factors. 
The  permanent  stratification  of  society  is  prevented  by  the 
rising  of  genius  from  the  lower  levels  and  the  sinking  of  medi- 
ocrity from  the  higher,  by  the  boiling  of  the  social  melting  pot, 
by  new  mutations  and  Mendelian  combinations,  all  of  which 
contribute  to  cast  down  the  mighty  from  their  seats  and  to 
exalt  those  of  low  degree.  In  the  past  history  of  mankind 
there  have  been  many  attempts  to  establish  hereditary  classes; 
where  now  are  the  castes  of  rulers  and  slaves,  statesmen  and 
soldiers,  scholars  and  priests,  craftsmen  and  farmers,  of  an- 
cient Egypt,  Assyria,  Greece,  and  Rome,  or  even  of  medieval 
Europe  ?  The  instincts  of  the  race  as  a  whole  are  against  the 
establishment  of  such  hereditary  classes  and  in  favor  of  demo- 
cratic equality  of  opportunity,  with  social  position  dependent 
upon  individual  merit  rather  than  upon  family  name  or  class 
privilege,  and  these  instincts  are  probably  sound  both  socially 
and  biologically. 

Some  advocates  of  eugenics  have  dreamed  of  the  establish- 
ment of  an  Intellectual  aristocracy  by  the  segregation  and 
intermarriage  of  the  most  highly  gifted  members  of  society, 
such  as  the  prize  scholars  in  colleges  and  universities.  No 
doubt  this  could  be  accomplished  if  some  power  could  bring 
about  such  segregation  and  propagation,  but  unless  these  prize 
scholars  combined  many  excellent  physical  and  social  qualities 
as  well  as  mental  ones  such  segregation  would  probably  lead 
to  very  unsatisfactory  results.  It  would  seem  to  be  better  for 
prize  scholars  to  marry  prize  athletes  and  thus  preserve  the 


I 


THE  TREND  OF  EVOLUTION  171 

general  all-round  excellence  of  the  race,  rather  than  to  attempt 
to  develop  an  intellectual  or  social  aristocracy. 

Decreasing  Birth-rate  of  Intellectual  Classes.  There  is  no 
doubt  that  intellectual  ability  is  an  inherited  trait,  in  spite  of 
the  fact  that  great  men  have  sometimes  come  from  unknown 
ancestors  and  unknown  men  from  great  ancestors.  Mental 
capacity  probably  depends  upon  a  number  of  inheritance 
factors,  and  occasionally  each  of  two  mediocre  parents  may 
supply  factors  which  the  other  lacks,  thus  giving  rise  to  an 
excellent  combination  which  is  the  initial  step  in  the  production 
of  a  great  man;  on  the  other  hand,  even  superior  parents  may 
sometimes  furnish  a  bad  combination  of  inheritance  factors, 
and  the  resulting  child  may  be  mediocre  or  inferior.  But 
Galton  has  shown  that  in  an  equal  number  of  distinguished 
and  undistinguished  families  there  are  about  five  hundred  times 
as  many  chances  that  a  distinguished  man  will  come  from  the 
former  as  from  the  latter.  No  doubt  environment  is  an  im- 
portant factor  in  the  development  of  intellect  but  the  possi- 
bilities of  such  development  are  marked  out  in  the  germ-plasm. 
Superior  intellectual  ability  is  inherited  no  less  than  inferior 
ability,  genius  no  less  than  feeble-mindedness. 

It  is  therefore  most  important  for  the  intellectual  progress 
of  the  race  that  the  more  intelligent  classes  should  increase 
and  multiply  and  that  the  less  intelligent  should  be  relatively 
less  fertile, — and  yet  the  reverse  of  this  is  true.  In  spite  of 
individual  exceptions,  the  graduates  of  our  colleges  and  uni- 
versities probably  represent  on  the  whole  the  most  intelligent 
portion  of  our  population ;  they  have  been  sifted  out  from  their 
less  gifted  fellows  by  the  grammar  schools,  high  schools,  and 
colleges,  until,  on  the  average,  they  are  a  very  highly  selected 
group.  But  this  group  is  not  perpetuating  itself.  The  aver- 
age number  of  children  per  graduate  of  Harvard  and  Yale 
for  the  years  1 881-1890  was  about  1.5.  Up  to  the  year  1901 
the  average  per  graduate  of  Vassar  and  Bryn  Mawr  was  about 


172  THE  EVOLUTION  OF  MAN 

.8,  of  Mt.  Holyoke  about  .7,  and  of  Smith  College  a  little 
less  than  .6.  In  other  words,  as  Cattell  says,  the  average 
graduate  of  Harvard  or  Yale  is  the  father  of  threq-fourths 
of  a  son  and  the  average  graduate  of  the  women's  colleges 
named  is  the  mother  of  rather  less  than  one  half  of  a  daughter. 
The  birth-rate  among  the  members  of  the  honor  society,  Phi 
Beta  Kappa,  is  much  lower  than  that  of  the  average  graduates, 
and  in  general  it  may  be  said  that  the  higher  the  intellectual 
attainments,  the  lower  is  the  average  birth-rate.  This  is  true 
not  only  of  college  graduates  but  of  the  more  intelligent  people 
generally.  Among  American  men  of  science,  Cattell  finds  that 
the  birth-rate  has  decreased  in  a  single  generation  from  4.66 
per  family  to  2.22.  Since  in  the  general  population  it  takes 
an  average  of  three  or  more  children  per  family  to  preserve 
present  numbers,  it  will  be  seen  that  these  highly  selected  lines 
are  dying  out.  And  as  rapidly  as  others  of  superior  intelli- 
gence rise  out  of  the  general  population  they  also  become  rela- 
tively infertile.  Thus  the  intellectual  cream  of  the  race  is 
continually  skimmed  off,  and  it  is  a  question  how  long  it  will 
continue  to  rise. 

There  is  great  enthusiasm  to-day  among  certain  people,  who 
are  generally  childless,  for  small  families;  the  race  is  to  be 
regenerated  by  birth  control.  But  this  "reform"  begins  among 
those  who,  because  of  good  hereditary  traits,  should  have  large 
families.  If  only  those  who  should  not  have  children  were  to 
practice  birth  control,  it  would  be  a  blessing  to  mankind,  but 
there  can  be  no  doubt  that  thus  far  it  has  greatly  reduced  the 
number  of  children  among  the  intelligent  and  prudent  classes, 
without  influencing  to  any  extent  the  birth-rate  among  the 
unintelligent  and  imprudent.  Whether  this  result  will  be  re- 
versed In  the  future  no  one  can  predict.  Alexander  Graham 
Bell  believes  that  It  will,  in  time,  benefit  the  race  by  eliminating 
those  among  the  intelligent  classes  who  are  lacking  in  parental 
instincts.     Irving  Fisher  says  there  are  three  possibilities  in 


THE  TREND  OF  EVOLUTION  173 

birth  control :  ( i )  it  may  cause  depopulation  and  ultimately 
extinction  of  the  human  race;  (2)  it  may  reduce  the  repro- 
duction of  the  prudent,  intelligent,  and  ambitious,  leaving  the 
imprudent  and  unintelligent;  (3)  it  may  cut  off  the  strain  of 
the  silly  and  selfish,  the  weak  and  inefficient.  There  is  little 
if  any  likelihood  that  the  first  of  these  possibilities  will  ever 
be  realized;  depopulation  may  result  in  certain  countries  but  it 
will  never  become  universal  through  birth  control.  The  second 
possibility  is  already  an  actuality  so  far  as  the  reduction  of  the 
birth-rate  among  the  most  progressive  people  is  concerned. 
It  does  not  seem  probable  that  the  third  possibility  can  greatly 
benefit  the  race  before  much  damage  has  been  done  by  the 
second.  Of  course  if  those  who  preach  and  practice  birth 
control  are,  when  measured  by  the  highest  standards,  silly, 
selfish,  weak,  or  inefficient  to  a  greater  degree  than  others, 
then,  and  then  only,  is  it  working  for  the  betterment  of  the 
race.  It  seems  incredible  that  people  of  good  hereditary  traits 
should  think  that  they  can  improve  the  human  breed  by  com- 
mitting racial  suicide.  ^'There  be  those  which  have  made 
themselves  eunuchs  for  the  kingdom  of  heaven's  sake,"  but 
when  before  in  the  history  of  the  world  have  sane  men  made 
themselves  eunuchs  in  order  to  win  the  kingdom  of  the  earth? 
Those  feminists  who  declare  that  they  would  rather  die  than 
have  children  have  made  their  choice  between  the  only  alter- 
natives possible, — death  to  their  lines  and  to  their  participa- 
tion in  the  future  of  the  race,  or  children. 

But  while  the  more  progressive  lines  are,  as  a  whole,  dying 
out,  the  general  population  of  this  country  and  of  the  world 
is  more  than  maintaining  itself,  and  the  less  intelligent,  inde- 
pendent, and  aggressive  portions  of  the  population  are  prob- 
ably increasing  most  rapidly  of  all.  Thus  the  Scriptures  are 
being  fulfilled  that  *'the  meek  shall  inherit  the  earth."  It  is 
often  said  that  a  high  birth-rate  among  the  lower  classes  Is 


174  THE  EVOLUTION  OF  MAN 

always  offset  by  a  high  death-rate,  but  in  civilized  society  this 

Is  by  no  means  the  case. 

In  a  recent  paper  of  great  interest  and  importance,  Pearl 
has  shown  that  the  'Vital  index,"  that  is,  th'e  ratio  of  births  to 
deaths  within  a  given  time,  differs  greatly  in  different  elements 
of  our  population;  it  is  lowest  among  the  old  American  stock, 
and  highest  among  the  foreign-born  population.  In  New  Eng- 
land and  in  New  York  State,  the  native  population  of  native- 
born  parents  produces  only  about  .8  or  .9  of  a  birth  for  each 
death,  while  in  the  country  at  large  "the  native  population 
produces  only  a  fraction  over  one  baby  for  each  death.  In 
other  words,  the  native  population  .  .  .  is  in  about  the  same 
state  as  France  before  the  war,  and  not  in  as  vigorous  a  state 
as  the  French  population  is  now."  As  contrasted  with  this,  he 
says,  "Generally  speaking,  the  foreign  population  produces  in 
this  country  approximately  two  babies  for  every  death." 

In  so  far  as  this  foreign  population  is  equal  in  quality  to  the 
native  stock  which  it  is  replacing  there  is  no  cause  for  alarm  in 
this,  and  except  for  sentimental  regrets  on  the  part  of  the  old 
American  stock,  it  may  be  welcomed  as  a  rejuvenating  factor, 
but  if  this  foreign  stock  is  in  the  main  inferior  in  quality  to 
that  which  it  is  replacing,  then  indeed  is  there  cause  for  con- 
cern. 

Race  Differentiation  vs.  Race  Amalgamation.  Another 
important  principle  in  past  evolution  which  is  being  reversed  in 
the  case  of  man  is  that  of  racial  isolation  and  differentiation. 
Since  all  types  of  mankind  interbreed  freely,  it  is  evident  that 
distinct  races  could  not  have  been  established  and  perpetuated 
except  by  the  aid  of  isolation,  chiefly  geographical.  On  the 
whole,  race  differentiation  has  made  for  progress;  it  has  led 
to  the  establishment  of  races  peculiarly  fitted  to  the  environ- 
ments in  which  they  are  found  and  it  has  favored  the  estab- 
lishment of  types  superior  in  certain  directions  though  they 
may  be  inferior  in  others. 


THE  TREND  OF  EVOLUTION  175 

However,  with  increasing  means  of  communication,  and  as 
a  result  of  migration  and  commercial  relations,  there  is  no 
longer  complete  geographical  isolation  of  any  people  and  the 
various  races  of  mankind  are  being  brought  into  closer  and 
ever  closer  contact.  Man  is  now  engaged  in  undoing  the  work 
of  hundreds  of  centuries;  if  in  the  beginning  God  *'made  of 
one  blood  all  nations  of  men,"  it  is  evident  that  man  is  now 
making  of  all  nations  one  blood.  In  the  United  States  prac- 
tically all  the  races  of  mankind  are  represented  and  a  study  of 
the  census  returns  shows  that  all  the  European  races  in  this 
country  are  being  rapidly  fused  together.  Pearl  has  recently 
shown  that  from  "one  fourth  to  one  half  as  many  children  are 
produced  in  a  given  year  from  mixed  matings  (in  which  one 
partner  is  American)  as  from  strictly  American-born  persons. 
Amalgamation  of  the  immigrant  elements  into  the  previously 
existing  complex  is  certainly  going  on  apace." 

The  ^'typical  American"  is  the  product  of  the  fusion  of 
various  European  races  and  we,  at  least,  believe  that  the  re- 
sults of  such  race  mixtures  are  good.  Even  European  races 
are  rarely  if  ever  pure,  but  represent  mixtures  of  many  dif- 
ferent stocks.  If  "pure"  English,  Irish,  Scotch,  Dutch,  Ger- 
man, Russian,  French,  Spanish,  or  Italian  lines  are  traced 
back  only  a  few  generations  they  are  found  to  include  many 
foreign  strains.  The  author  of  Robinson  Crusoe  wrote  two 
centuries  ago  of  the  "True-born  Englishman" : 

These  are  the  heroes  that  despise  the  Dutch, 
And  rail  at  new-come  foreigners  so  much; 
Forgetting  that  themselves  are  all  derived 
From  the  most  scoundrel  race  that  ever  lived; 
A  horrid  crowd  of  rambling  thieves  and  drones 
Who  ransacked  kingdoms,  and  dispeopled  towns; 
The  Pict,  and  painted  Briton,  treach'rous  Scot, 
By  hunger,  theft,  and  rapine,  hither  brought; 


176  THE  EVOLUTION  OF  MAN 

Norwegian  pirates,  buccaneering  Danes, 
Whose  red-haired  offspring  everywhere  remains; 
Who,  join'd  with  Norman  French,  compound  the  breed 
From  whence  your  "true-born  Englishmen"  proceed. 

Even  the  primary  races  of  mankind  are  rapidly  fusing  in 
many  parts  of  the  world.  In  the  United  States  from  15  to  20 
per  cent  of  the  total  negro  population  of  about  10,500,000  are 
mulattoes  and  these  are  increasing  more  rapidly  than  the  pure 
blacks.  In  South  American  countries  it  has  been  estimated 
that  there  are  about  26,000,000  whites,  Indians,  and  negroes, 
and  about  20,000,000  of  mixed  blood.  In  Australia  and  New 
Zealand,  after  only  a  little  more  than  a  century  of  contact 
with  the  whites,  there  are  about  as  many  "half  castes'*  as  full- 
blooded  aborigines.  Similar  tendencies  to  amalgamation  of 
the  primary  races  are  found  in  Mexico,  the  West  Indies, 
Africa,  Indo-China,  the  islands  of  the  Pacific,  and  in  other 
parts  of  the  world.  It  is  said  that  there  are  no  cases  in  his- 
tory where  two  races,  however  different,  have  for  long  occu- 
pied the  same  territory  and  yet  have  preserved  their  racial 
purity.  Even  the  Jews,  who  are  a  peculiarly  separate  and 
distinct  race,  have  received  large  admixtures  of  Gentile  blood 
in  every  country  in  which  they  have  lived.  Fishberg  says  that 
in  western  Europe,  America,  and  Australia  from  25  to  50  per 
cent  of  all  Jews  who  marry,  marry  non-Jews. 

If  this  movement  goes  on,  as  we  have  every  reason  to  expect 
that  it  will,  it  can  only  end  in  the  more  or  less  complete  fusion 
of  existing  races,  and  it  needs  only  the  vision  that  can  look 
ahead  a  few  thousand  years  at  most  to  see  all  races  blended 
into  a  common  stream.  What  the  results  of  such  fusion  may 
be  we  can  only  guess,  though  its  effects  in  ancient  Egypt, 
Greece,  Italy,  and  more  recently  in  various  countries  of 
eastern  Europe,  the  West  Indies,  Mexico,  and  South  America 
are  by  no  means  reassuring.     Hybrids  are  not  necessarily  in- 


THE  TREND  OF  EVOLUTION  177 

ferior,  and  they  are  sometimes  superior  to  either  of  the  parent 
races.  MendeHan  inheritance  holds  good  in  the  crossing  of 
human  races  as  well  as  everywhere  else  and  It  leads  to  all 
kinds  of  combinations  of  the  qualities  of  the  parents.  Accord- 
ingly some  hybrids  may  be  expected  to  show  the  bad  qualities 
of  both  parent  races  while  others  show  the  good  qualities  of 
both,  but  it  is  practically  certain  that  the  general  or  average 
result  of  the  crossing  of  a  better  and  a  poorer  race  is  to  strike 
a  balance  somewhere  between  the  two. 

If  only  good  ore  goes  into  the  "melting  pot"  there  is  no 
cause  to  fear  for  the  result;  and  if  those  hybrids  which  com- 
bine the  good  qualities  of  the  parent  races  could  be  segregated 
and  bred,  a  race  superior  to  any  existing  human  type  could 
probably  be  established.  This  is  just  the  method  followed  by 
breeders  in  the  production  of  improved  races  of  plants  and 
animals,  many  of  which  are  the  products  of  deliberate  hybridi- 
zation. But  the  breeder  ruthlessly  eliminates  inferior  stock 
and  breeds  only  from  the  best,  and  If  by  some  similar  process 
it  were  possible  to  eliminate  from  reproduction  the  inferior 
racial  combinations  and  to  perpetuate  the  best,  we  might  expect 
to  get  from  this  great  experiment  in  human  hybridization  a 
very  superior  breed  of  men  combining  the  good  qualities  of  all 
the  constituent  races.  It  seems  very  doubtful  whether  any  such 
result  as  this  will  ever  be  attained,  and  in  the  absence  of  such 
selection  and  segregation  the  general  result  of  race  amalgama- 
tion must  be  an  averaging  of  the  qualities  of  the  parent  races. 

The  character  of  a  composite  race  will  depend  not  only  upon 
the  qualities  but  also  upon  the  relative  numbers  of  the  races 
which  enter  into  it,  and  the  latter  will  depend  upon  the  present 
numbers  of  existing  races,  their  rate  of  Increase,  cultural  de- 
velopment, and  the  habitable  portions  of  the  globe  which  they 
control.  In  all  of  these  respects  the  white  races  hold  the  lead, 
followed  in  turn  by  the  yellow,  the  brown,  the  black,  and  the 
red  races,  and  It  is  evident  that  unless  the  white  races  destroy 


178  THE  EVOLUTION  OF  MAN 

one  another,  commit  race  suicide,  or  die  at  the  top,  they  are 
destined  to  furnish  the  principal  contribution  to  the  future 
population  of  the  globe. 

The  Limits  of  Population.  Finally,  the  human  population 
of  the  world  is  rapidly  approaching  Its  maximum — for  while 
populations  tend  to  Increase  continually  the  limits  of  the  habi- 
table globe  remain  fixed  and  the  means  of  subsistence  are  sub- 
ject to  the  law  of  diminishing  returns.  Pearl  estimates  that 
within  200  years  the  population  of  the  United  States  will  have 
reached  its  maximum  of  about  200,000,000.  Alfred  Marshall 
calculates  that  the  population  of  the  entire  world  will  have 
reached  its  maximum  of  about  6,000,000,000  in  200  years. 
These  estimates  assume  that  increase  of  population  and  of 
means  of  subsistence  will  In  the  future  conform  to  the  same 
mathematical  formulae  as  hitherto, — an  assumption  that  is 
probably  justified.  If  these  estimates  are  correct  the  grand- 
children or  great-grandchildren  of  persons  now  living  may  see 
the  maximum  population  of  this  country,  and  perhaps  of  the 
world,  attained.  Even  if  by  means  of  greatly  improved  agri- 
culture or  by  revolutionary  scientific  discoveries  this  time 
should  be  doubled  it  would  still  be  a  relatively  short  period 
before  the  limits  of  the  possible  population  of  the  globe  would 
be  reached.  Thereafter  the  population  will  remain  stationary, 
either  through  increase  of  the  death-rate  or  decrease  of  the 
birth-rate.  Under  these  conditions  it  is  probable  that  both 
natural  and  artificial  selection  will  be  intensified.  It  Is  reason- 
able to  expect  that  on  the  whole  natural  selection  will  make 
for  progress  and  it  does  not  seem  probable  that  artificial  means 
of  limiting  population  will  continue  to  cut  off  the  better  stocks 
and  to  favor  the  worse. 

There  is  ground  to  hope,  therefore,  that  in  a  crowded  globe 
both  natural  and  artificial  selection  will  make  for  the  improve- 
ment of  the  race,  but  such  Improvement  is  likely  to  be  slow  and 
painful.     Natural  selection,  under  various  aspects,  is  still  the 


THE  TREND  OF  EVOLUTION  179 

most  potent  factor  in  directing  evolution  though  it  is  extremely 
slow  in  its  action  and  excessively  wasteful.  There  is  reason  to 
hope  that  in  the  near  future  intelligent  human  selection  may 
cooperate  with  natural  selection,  thus  rendering  progress  more 
rapid  and  more  merciful.  Certainly  eugenical  education  should 
begin  to  bear  fruit, — that  is,  more  children  of  the  better  sort 
and  fewer  of  the  worse  variety, — within  the  next  generation. 
Unless  it  does  we  may  be  sure  that  the  time  will  come  when  in 
a  crowded  globe  natural  selection  will  reassert  itself  and  there 
will  be  a  return  to  "nature's  simple  plan"  of  promoting  fitness 
by  the  ruthless  elimination  of  the  unfit. 

The  Immediate  and  the  Distant  Future 

The  Immediate  Future.  In  the  midst  of  all  these  condi- 
tions and  tendencies  of  the  human  race, — the  decreasing  in- 
fluence of  natural  selection,  the  retrogressive  selection  of 
civilization,  the  decreasing  birth-rate  of  the  more  intelligent 
classes,  the  Increasing  amalgamation  of  races,  the  rapid  ap- 
proach of  the  time  when  the  earth  will  be  fully  populated  and 
its  natural  resources  exhausted  or  greatly  diminished, — In  the 
whirl  of  all  these  changes  it  does  not  seem  probable  that  human 
evolution  will  long  remain  stationary.  On  the  whole,  It  must 
be  admitted  that  these  tendencies  do  not  point  to  racial  prog- 
ress, and  some  of  them  presage  retrogression,  degeneration, 
and  decay  unless  they  can  be  overcome. 

There  is  much  In  the  modern  world  that  reminds  one  of  the 
period  of  decline  of  former  civilizations,  and  especially  of 
Greece  and  Rome,  and  many  persons  have  wondered  whether 
our  civilization  is  not  traveling  the  downward  road  to  a  similar 
end.  In  both  Greece  and  Rome  the  decline  was  preceded  by 
a  large  amount  of  race  mixture,  and  a  decreasing  birth-rate 
among  the  higher  classes,  while  It  remained  relatively  un- 
changed elsewhere.  Momsen  says  that  the  decay  of  Rome 
was  due  mainly  to  **the  difference  between  the  fertility  of  the 


i8o  THE  EVOLUTION  OF  MAN 

higher  and  the  poorer  classes."    Tenny  Frank^  concludes  that 

In  Nero's  day,  about  90  per  cent  of  the  plebeians  on  the  streets 

of  Rome  had  oriental  blood,  while  the  whole  Empire  was  a 

"melting  pot"  In  which  the  oriental  was  a  large  part  of  the 

ore: 

Race  suicide  curtailed  the  stock  of  the  more  sophisticated, 
the  aristocracy,  and  the  rich.  Before  our  day,  only  at  Greece 
and  Rome  was  reproduction  under  rational  control  and  there 
the  race  went  under.  Of  forty-five  patricians  In  Caesar's  day 
only  one  is  represented  by  posterity  when  Hadrian  came  to 
power.  Of  the  families  of  nearly  four  hundred  senators  re- 
corded In  65  A.  D.  under  Nero,  all  trace  of  a  half  is  lost  by 
Nerva's  day,  a  generation  later.  The  voluntary  choice  of 
childlessness  accounts  largely  for  the  unparalleled  condition — 
and  is  probably  the  most  important  phase  of  the  whole  question 
of  the  change  of  race. 

A  striking  parallel  to  what  Is  found  In  most  of  the  civilized 
world  to-day!  Whatever  may  have  been  the  causes  of  the 
decline  of  former  civilizations.  It  is  plain  that  there  were  left 
In  other  parts  of  the  world  strong  human  reserves  that  could 
carry  forward  the  standard  of  civilization  which  was  dropped 
by  a  dying  race.  But  in  a  world  where  practically  all  western 
nations  are  suffering  from  this  sickness  of  civilization,  and  In 
which  racial  amalgamation  Is  fusing  all  into  a  common  type, 
where  are  the  reserves  that  can  be  rallied  to  the  standard,  if 
civilization  should  again  decay?  If  history  should  repeat 
Itself  and  the  western  nations  should  go  down  as  did  Greece 
and  Rome,  possibly  Russia,  or  China,  or  Japan  might  take  up 
the  banner  and  civilization  once  more  begin  Its  westward 
march  around  the  world. 

But  there  Is  this  important  difference  between  present  con- 
ditions and  those  of  any  former  age, — our  knowledge  of  and 

control  over  nature  are  vastly  greater  than  ever  before  and  the 

i 

^American  Historical  Revieiv,  21,  1916. 


THE  TREND  OF  EVOLUTION  i8i 

means  of  increasing  and  diffusing  knowledge  were  never  so 
good  as  at  present.  If  knowledge  and  education  can  save 
the  race  the  prospect  is  promising,  for  they  were  never  before 
so  widespread;  the  possibilities  of  continued  progress  rest  on 
education,  eugenics,  and  enlightened  effort. 

Education  is  the  first  and  most  important  step  in  combating 
these  tendencies  to  racial  decline.  Assuming  that  the  social 
instincts  of  the  major  portion  of  mankind  are  sound  and  that 
there  is  sufficient  intelligence  in  the  race  at  large  to  recognize 
the  dangers  that  threaten,  it  ought  to  be  possible  by  education 
to  meet  these  dangers  and  overcome  them.  A  more  thorough 
and  widespread  knowledge  of  the  nature  of  man  and  of  the 
principles  of  heredity  and  development  would  lead  to  the 
elimination  of  many  of  these  dangers,  for  in  the  main  we  have 
sinned  through  ignorance.  Such  knowledge  would  prevent  the 
importation  and  propagation  of  physical,  mental,  and  moral 
degenerates;  it  could  prevent  the  amalgamation  of  better 
races  and  families  with  poorer  ones;  it  should  increase  the 
number  of  good  matings  and  of  superior  children;  and  it 
should  make  human  life  healthier,  happier,  more  rational,  and 
more  efficient.  Whatever  good  may  come  to  the  race  through 
better  legislation,  sanitation,  eugenics,  or  euthenics  will  be 
made  possible  by  better  education. 

What  part  eugenics  may  play  in  the  betterment  of  the  hu- 
man race  cannot  now  be  foreseen.  There  is  no  doubt  that,  by 
means  of  a  thoroughgoing  system  of  eugenics,  feebleness  of 
•  body  and  of  mind  could  be  largely  reduced  and  the  race  as  a 
whole  made  more  healthful  and  intelligent;  in  short,  the  gen- 
eral average  of  the  race  could  be  raised  more  nearly  to  the 
level  of  the  most  perfect  men  and  women  of  the  past  or 
present.  It  Is  doubtful  whether  eugenics  can  go  farther  than 
this  and  there  is  no  probability  that  it  can  ever  produce  a  race 
of  supermen.  Important  as  eugenics  Is  in  preventing  racial 
degeneration  it  does  not  hold  forth  the  hope  of  endless  human 


1 82  THE  EVOLUTION  OF  MAN 

progress.  For  the  present  at  least  the  most  that  it  can  do  is 
to  take  the  place  of  natural  selection  in  limiting  the  propaga- 
tion of  the  feeble-bodied  and  the  feeble-minded  and  in  favoring 
that  of  the  strong  and  sane.  This  would  at  once  preserve  and 
perpetuate  the  best  human  lines  and  would  in  time  raise  the 
average  of  the  race  as  a  whole  but  probably  it  would  not  pro- 
duce a  new  and  better  species  of  man.  The  eugenist  can 
neither  produce  new  mutations  nor  does  he  know  what  muta- 
tions or  new  combinations  of  characters  will  be  most  useful 
and  most  viable  in  future  ages.  If  the  fads  and  fancies  of 
reformers  could  be  established  in  the  germ-plasm  and  all  men 
could  be  made  eugenically  equal  the  whole  race  might  come  to 
a  rapid  end.  It  is  probably  fortunate  that  men  are  not  charged 
with  the  duty  of  directing  future  evolution,  and  we  can  only 
hope  that  nature,  which  has  directed  progressive  evolution 
from  amoeba  to  man,  without  human  guidance,  may  work 
still  greater  wonders  in  future  ages. 

Finally  the  lesson  of  past  evolution  teaches  that  there  can 
be  no  progress  of  any  kind  without  struggle ;  in  physical  evolu- 
tion progress  has  come  through  the  struggle  for  existence  and 
for  more  abundant  life ;  in  intellectual  evolution,  through  striv- 
ings for  freedom  and  enlightenment;  in  social  evolution, 
through  the  victory  of  social  instincts  and  ideals  over  anti- 
social ones.  The  improvement  of  the  human  race,  if  not  the 
further  evolution  of  man  will  depend  in  part  upon  enlightened 
human  effort.  To  us  it  is  given  to  cooperate  in  this  greatest 
work  of  all  time  and  to  have  a  part  in  the  triumphs  of  future 
ages,  not  merely  by  improving  the  conditions  of  individual  life 
and  development  and  education,  but  much  more  by  improving 
the  ideals  of  society  and  by  breeding  a  better  race  of  men  who 
will  "mold  things  nearer  to  the  heart's  desire." 

The  Distant  Future.  What  the  distant  future  may  hold  in 
store  for  the  human  race  we  can  only  guess.  It  may  be  that 
the  entire  race  will  become  extinct  and  leave  the  dominance  of 


THE  TREND  OF  EVOLUTION  183 

the  earth  to  other  living  things.  Although  this  has  been  the 
history  of  many  dominant  species  in  the  past  it  does  not  seem 
probable  that  It  will  be  the  fate  of  man,  for  he  is  able  to  adapt 
himself  to  changed  conditions,  to  modify  his  environment,  and 
to  control  his  destiny  as  no  other  creature  that  has  ever  lived 
on  the  earth  has  been  able  to  do.  If  conditions  of  life  should 
ever  become  so  adverse  that  the  entire  human  race  should  be- 
come extinct  we  may  probably  assume  that  all  other  higher 
animals  would  also  perish. 

It  Is  possible  that  the  entire  race  may  suffer  retrogressive 
evolution  and  return  to  a  less  highly  organized  condition. 
Many  other  types  of  animals  have  passed  the  climax  of  their 
evolution  and  have  then  declined  and  their  degenerate  repre- 
sentatives still  survive.  But  in  these  cases  other  forms  better 
fitted  for  survival  have  taken  their  places  and  progress  has 
continued  in  other  lines.  Intellectual  and  social  evolution  has 
reached  a  climax  in  man  and  it  has  so  greatly  increased  his 
control  over  himself  and  his  environment  that  it  seems  scarcely 
possible  that  it  will  universally  and  permanently  decline  and  be 
replaced  by  less  adaptable  and  less  efficient  characters. 

Perhaps  in  future  ages  the  progressive  evolution  of  man  will 
continue,  somewhere  and  somehow.  If  higher  species  of  man 
evolve  in  the  future  it  is  not  unlikely  that  this  will  occur,  as  in 
the  past,  in  connection  with  great  secular  changes,  over  which 
man  has  no  control,  such  as  the  rising  and  sinking  of  conti- 
nents, the  formation  of  deserts  or  mountains  or  oceans,  or 
changes  in  climate  comparable  to  the  glacial  and  interglacial 
epochs,  during  which  human  evolution  made  such  wonderful 
progress. 

In  the  present  conditions  and  tendencies  of  the  human  race, 
in  the  contest  between  progressive  and  retrogressive  forces, 
we  see  much  cause  for  anxious  concern,  but  thinking  on  the 
distant  past  and  the  boundless  future  creates  a  feeling  of  de- 
tachment and  of  philosophic  calm  like  that  of  the  dwellers  on 


1 84  THE  EVOLUTION  OF  MAN 

Olympus.  We  cannot  see  clearly  the  next  scene,  we  can  scarcely 
imagine  the  next  act,  and  the  end  of  the  great  Drama  of  Evo- 
lution, if  there  is  to  be  an  end,  is  a  matter  of  faith  alone. 

O,  yet  we  trust  that  somehow  good 

Will  be  the  final  goal  of  ill. 

To  pangs  of  nature,  sins  of  will, 
Defects  of  doubt  and  taints  of  blood. 


BIBLIOGRAPHY 

CONTAINING  A  SELECTED  LIST  OF  REFERENCES  FOR  EACH 
CHAPTER  OF  THE  BOOK 

CHAPTER  I 

Churchward^   A.     The   origin   and  evolution  of  the  human   race. 

New  York  and  London,  1922. 
Dubois^    Eugene.      Pithecanthropus    erectus,    ein    menschenaehnliche 

Uebergangsform.     Batavia,  1894. 
Elliot,  G.  F.  Scott.     Prehistoric  man  and  his  story.    London,  1915. 
Gregory,  W.  K.    The  origin  and  evolution  of  the  human  dentition:  a 

palaeontological  review.     Journal  of  Dental  Research,  Vol.  2,  Nos. 

1-4,  1920;  Vol.  3,  No.  1,  1921. 
Hrdlicka,  Ales.     Skeletal  remains  suggesting  or  attributed  to  early 

man  in  North  America.    Bureau  of  American  Ethnology,  Bulletin  33, 

1907. 
The  most  ancient  skeletal  remains  of  man.    Annual  Report  of  the 

Smithsonian  Institution  for  1913,  pp.  491-552,  1914;  2d  ed.,  1916. 
Keith,  Sir  Arthur.    The  antiquity  of  man.    London,  1915. 
On  the  Broken  Hill  skull.     London  Illustrated  News,  November 

19,  1921,  p.  686. 
Lull,  R.  S.     Organic  evolution.     New  York,  1917. 
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Haven,  1918. 
MacCurdy,  G.  G.     Eolithic  and  Paleolithic  man.    American  Anthro- 
pologist, new  series,  Vol.  11,  pp.  92-100,  1909. 
Recent   discoveries  bearing  on   the   antiquity  of  man   in   Europe. 

Annual  Report  of  the  Smithsonian  Institution  for  1909,  pp.  531-583, 

1910. 
OsBORN,  H.   F.     Men  of  the  Old  Stone  Age.     New  York,  3d  ed., 
1919. 


1 86  THE  EVOLUTION  OF  MAN 

The  Pliocene  man  of  Foxhall  in  East  Anglia.     Natural  History, 

November-December,  1921,  pp.  565-576. 
The  dawn  man  of  Piltdown,  Sussex.    Ibid.,  pp.  577-590. 


Reinach^  Salomon.    Repertoire  de  Tart  quaternaire.     Paris,  1913. 

RuTOT,  A.    La  prehistoire.     1918. 

ScHOETENSACK^   Otto.     Der   Unterkiefer   des  Homo   heidelbergensis, 

Leipzig,  1908. 
SoLLAS^  W.  J.     Ancient  hunters.     London,  1915. 
Woodward^  A.  Smith.    On  the  Broken  Hill  skull.    London  Illustrated 

News,  November  19,  1921,  p.  682. 
A  new  cave  man  from  Rhodesia,  South  Africa.    Nature,  November 


17,  1921,  p.  371. 


CHAPTER  II 


Bardeen^  C.  R.  Height  and  weight  in  relation  to  build  during  post- 
natal development.  Carnegie  Contributions  to  Embryology,  Vol.  9, 
No.  46,  1920. 

Daffner^  F.  Das  Wachstum  des  Menschen ;  anthropologische  Studien. 
Leipzig,  1902. 

Deniker^  J.  The  races  of  man,  an  outline  of  anthropology  and  ethnog- 
raphy.   London,  1900. 

Donaldson^  H.  H.  The  growth  of  the  brain.  London  and  New 
York,  1903. 

Duckworth^  W.  L.  H.  Morphology  and  anthropology.  Cambridge, 
1915. 

Ellis^  H.  Man  and  woman,  a  study  of  human  secondary  sex  characters. 
5th  ed.,  London,  1914. 

Hall,  G.  Stanley.    Senescence,  the  last  half  of  life.    New  York,  1922. 

Jackson,  C.  On  the  prenatal  growth  of  the  human  body,  etc.  Amer. 
Jour,  of  Anat.,  Vol.  9,  1909. 

Keith,  Sir  Arthur.  Human  embryology  and  morphology.  3d  ed., 
London,  1913. 

MiNOT,  C.  S.  The  problem  of  age,  growth  and  death;  a  study  of 
cytomorphosis.    New  York,  1908. 

Prentiss  and  Arey.  Text-book  of  embryology.  3d  ed.,  Philadelphia, 
1920. 


I 


BIBLIOGRAPHY  187 

Ranke,  J.    Der  Mensch.    2  vols.    Leipzig,  1887. 
Stratz^  C.  H.     Naturgeschichte  des  Menschen:  Grundriss  der  Soma- 

tischen  Anthropologie.     Stuttgart,  1904. 
WiEDERSHEiM,  R.    The  structure  of  man,  an  index  to  his  past  history. 

London,  1895. 

CHAPTER  III 

Berman^  L.    Glands  regulating  personality.    New  York,  1922. 
Cannon^  W.   B.     Bodily  changes   in  pain,   hunger,   fear,   and  rage. 

New  York,  1915. 
CoNKLiN^  E.  G.     Heredity  and  environment  in  the  development  of 

man.     Princeton,  1920. 
Foster^  M.    Lectures  on  the  history  of  physiology.     Cambridge,  1901. 
Haldane^  J.  S.     Mechanism,  life  and  personality.     New  York,  1914. 
Organism   and   environment   as   illustrated   by   the   physiology   of 

breathing.    New  Haven,  1917. 
Myerson^  a.    The  foundations  of  personality.    Boston,  1921. 
Parker^  G.  H.    The  reactions  of  sponges,  with  a  consideration  of  the 

origin  of  the  nervous  system.    Jour.  Exper.  Zool.,  Vol.  8,  1910. 
^The  origin  and  significance  of  the  primitive  nervous  system.     Proc. 

Amer.  Philos.  Soc,  Vol.  50,  1911. 

Biology  and  social  problems.    Boston,  1914. 

-The  elementary  nervous  system.     Philadelphia,  1919. 


Robinson,  J.  H.    The  mind  in  the  making.    New  York,  1921. 
Schafer,  E.  a.     The  endocrine  organs.     London,  1916. 


CHAPTER  IV 

CoNKUN,  E.  G.    The  direction  of  human  evolution.    New  York,  1921. 
Heredity  and  environment  in  the  development  of  man.     Princeton, 

1920. 
OsBORN,  H.  F.     Men  of  the  Old  Stone  Age,  their  environment,  life 

and  art.     3d  ed.,  New  York,  1919. 
Boas,  Franz.    The  mind  of  primitive  man.    New  York,  1913. 
Keller,  A.  G.     Societal  evolution.     New  York,  1915. 


1 88  THE  EVOLUTION  OF  MAN 

Angell^  J.  R.     Chapters  from  modern  psychology.     New  York,  1912. 

Watson^  J.  B.  Behavior — Introduction  to  comparative  psychology. 
New  York,  1914. 

Thorndike,  E.  L.    Animal  intelligence.     New  York,  1911. 

Washburn,  M.  F.    The  animal  mind.    2d  ed..  New  York,  1917. 

Jennings,  H.  S.    Behavior  of  the  lower  organisms.    New  York,  1915. 

LoEB,  J.  Comparative  physiology  of  the  brain  and  comparative  psy- 
chology.   New  York,  1900. 

Forced  movements,   tropisms  and  animal  conduct.      Philadelphia, 


1918. 


CHAPTER  V 


Sumner,  W.  G.    Folkways.    Boston,  1907. 

Collected  Essays.    4  vols.     New  Haven,  1914-1918. 

What  social  classes  owe  to  each  other.     New  York,  1911. 

Keller,  A.  G.     Societal  evolution.     New  York,  1915. 

Through  war  to  peace.     2d  ed..  New  York,  1921. 

Colonization.     Boston,  1908. 

Bagehot,  W.     Physics  and  politics.     New  York,  1902. 
Darwin,  C.  R.    Descent  of  man.     New  York,  1898. 
Galton,  Sir  F.     Hereditary  genius.     New  York,  1870. 

Essays  in  eugenics.     London,  1909. 

GuMPLOWicz,  L.     Der  Rassenkampf.     Innsbruck,  1883. 

Haycraft,  J.  B.     Darwinism  and  race  progress.     2d  ed..  New  York, 

1900. 
Holmes,  S.  J.    The  trend  of  the  race.    New  York,  1921. 
Huxley,  T.  H.    Man's  place  in  nature.    Collected  Essays,  New  York, 

1901. 
LiPPERT,  J.     Kulturgeschichte   der   Menschheit.     2   vols.      Stuttgart, 

1886. 
ScHALLMAYER,  W.    Vererbung  und  Auslese  im  Lebenslauf  der  Volker. 

Jena,  1903. 
Seward,  A.  C.   (editor).     Darwin  and  modern  science.     Cambridge, 

1909. 
Spencer,  Herbert.    Principles  of  sociology.    3  vols.    New  York,  1877- 

1896. 


BIBLIOGRAPHY  189 

CHAPTER  VI 

Bell^  a.  G.  Is  race  suicide  possible?  Jour.  Heredity,  Vol.  11,  1920. 
CoNKLiN^  E.  G.  The  direction  of  human  evolution.  New  York,  1921. 
Darwin^  C.  R.     The  origin  of  species  by  means  of  natural  selection, 

etc.    New  York,  1898. 
The  variation  of  animals  and  plants  under  domestication.     2  vols. 

London,  1905. 
The  descent  of  man.    2d  ed.,  New  York,  1898. 


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1921. 
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International  Monthly,  Vol.  4,  1901. 
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21,  1916. 
Galton^  Sir  F.     Hereditary  genius.    New  York,  1870. 

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Holmes^  S.  J.    The  trend  of  the  race.     New  York,  1921. 

Huxley^  T.  H.    On  the  natural  Inequality  of  men.     Collected  Essays, 

New  York,  1901. 
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1919. 
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Sciences,  Vol.  15,  1920. 


INDEX 


Abbott,  Lewis,  22 

Ability,    intellectual,    inherited    trait, 

171 
Acceleration,  prepubertal,  69 
Acquired    characteristics,    inheritance 

of,  156-157 
Acromegaly,  64 
Actions,  intelligent,  105,  119 

mechanical,  105 

reflex  and  instinctive,  theory  of  the 
origin  of,  107 

tropisms,  105 

volitional,  100 
Activities,  control  of  bodily,  84 
Adams,  Henry,  126,  128 
Adaptation,  intelligent,  106 
Adaptive  reactions,  113 
Adjustment,  automatic,  150 

cultural,  136 

Darwinian  theory  of,  126 

human,  134 

intelligent,  119,  150 

material,  133 

societal,  136 
Adjustors,  84,  86 

Africa,  racial  amalgamation  in,  176 
Age,  Chellean,  22 

Mesozoic,  19 

of  Pithecanthropus,  16 

Pliocene,  9 

Upper  Siwalik,  16 
Alimentary  canal,  development,  49 

organs  developing  from,  52 
Alterations,  chemical,  in  senescence,  71 
Amalgamation  of  races,  175 
Amalgamation,  tendency  to,  176 


Ameghino,  F.,  10 

American,  typical,  175 

Amnion,  57 

Amniotic  cavity,  43 

Amoeba,  105,  112,  153 

Analogy,  129 

Anatomical  variations,  75-78 

Animal,  consciousness,  theory  of,  112 

fitness,  135 

intelligence,  104-112 

life,  changes  in,  104 

reactions,  121 

size,  63 

behavior  of,  108 
Animals,  invertebrates,  39 

mammals,  39 

metazoa,  39 

protozoa,  39 

vertebrate,  39 
Ant,  instincts  of,  108 
Anthropophagy,  144 
Anthropoids  and  man,  Huxley's  com- 
parison, 131 

phylogeny,  36 
Anti-bodies,  see  Hormones 
Antiquity,  means  of  determining,  8 
Appendix,  comparison   of,   in   various 
animals,  74 

vermiform,  73,  74 
Archipallium,  46,  93 
Areas,  association,  of  brain,  120 

frontal,  of  brain,  120 
Aristotle,  81 
Art,  Aurignacian,  34 
Art,  Cro-Magnon,  32 


192  INDEX 

Arteries,  development,  52 

hardening  of,  70 
Arteriosclerosis,  70 
Asia,  birthplace  of  mankind,  5 
Association  areas  of  brain,  120 
Association,  inheritance,  157,  163 
Assortative  mating,  169 
Attica,  New  York,  11 
Auricle,  of  heart,  51 

Bacillus  bulgaricus,  71 
Bagehot,  W.,  145 
Banderlog,  the,  109 
Banolas,  Spain,  24 
Bee,  instincts  of,  108 
Behavior  of  animals,  108 

of  man,  120 

instinctive,  105 

intelligent,  110,  122 
Bell,  A.  G.,  172 
Birds,  nesting  instincts  of,  108 
Birth,  60 
Birth  control,  172 

eflfects  of,  173 
Birth-rate,  171-174 

American  scientists,  172 

of  college  graduates,  171 

of  intellectual  classes,  171-174 

Phi  Beta  Kappa,  172 
Birth,  ratio  to  deaths,  174 
Births,  multiple,  62 

proportion  of  male  and  female,  62 
Blood  cells,  development,  52 

natural  history,  52 
Blood  vessels,  development,  52 
"Blue  baby,"  60 
Blumenbach's  classification,  40 
Body  cavity,  see  Ccelom 
Body  proportions,  changes  in   during 

growth,  65 
Body  wall,  formation  of,  45 
Bone,  growth  of,  67 

growth  shown  by  madder,  67 
Bones,  cranial,  ossification  of,  55 


Boule,  Marcelin,  24 

Boy,  growth  of,  67-69 

Brain  cells,  number  in  cortex,  93 

Brain,  cortex,  93,  120 

Breuil,  I'Abbe,  34 

Broken  Hill  mine,  Rhodesia,  28 

Bronze,  age  of,  2 

Bushmen,  Africa,  12 

Caecum,  73,  74 

comparison  in  various  animals,  74 
Cancer,  65 

Cannibalism,  136,  144 
Capacity,  human,  122 
Capacity,  mental,  dependent  on  inherit- 
ance factors,  171 
Capillaries,  development,  52 
Carbon,  99 
Catholicism,  144 
Cattell,  172 

Cavern,  Lost  Hope  Inlet,  11 
Celibacy,  169 
Cells,  39 

interstitial,  97 
Cerebral  cortex,  93 

atrophy,  71 

center  of  sensation,  82 
Cerebral  sacs,  45 
Changes,     retrogressive     in     various 

organs,  73-75 
Characteristics,    acquired,    inheritance 
of,  156-157 

of  soma,  157 
Child,  change  in  proportions,  65 
Chimpanzee,  fossil,  20 
Chorion,  57 
Chronological  table,  4 
Chronology,  European,  3 
Churchward,  A.,  12 
Circulation,  change  at  birth,  60 
Civilization,  115,  134,  158 

European,  115 

evidence  of,  118 

pre-Columbian,  11 


INDEX 

selection 


193 


Civilization,     retrogressive 

of,  168-171 
Clarke,  Dr.  J.  M.,  11 
Classes,  hereditary,  170 

intellectual,  birth  rate  of,  171-174 
Classification,  of  human  races,  40 
Cleft  palate,  57 
Coccyx,  11 
Cochlea,  48 

Code,  new,  of  adjustment,  144 
Codes,  collision  of,  144 

rational  selection  of,  146 
Coelom,  44 
Collyer,  36 
Combinations,    Mendelian,    154,    155, 

170 
Competition,  between  societies,  143 

tragedies  of,  145 
Conduct,  134 

rational,  105 
Congenital  imperfection,  167 
Consciousness,  and  experience,  113 

and  intelligence,  112-114 
Control,  voluntary,  lack  of  in  certain 

actions,  106 
Conversion,  sexual,  97 
Conviction,  ex  parte;  148 
Cortex,  of  brain,  120 

cerebral,  93 
Counter-selection,  135 
Cranial  sutures,  disappearance  of,  67 
Creation,  Mosaic  account  of,  1 
Creeping,  sea-anemone,  88 
Cretinism,  64 
Cro-Magnon  man,  31 

art,  32 

decline,  35 

implements,  32 

size,  32 

skull,  32 

skull  and  face,  33 

skull,    compared    with    Neandertal 
man,  25 


Cromer  flints,  4 

Cultural  adjustment,  135,  136 

societal,  135 
Custom,  136 

Darling  Downs,  Australia,  12 
Darivin  and  modern  science,  131 
Darwin,  C.  R.,  128,  131 

formulation  of  natural  selection,  158 

on  variation,  156 
Darwinian  factors,  130,  136 

theory,  131 
Dawson,  Charles,  20,  22 
Deaths,  ratio  to  births,  174 
Degeneracy  in  certain  families,  168 
Degeneration,  senile,  see  Senescence 
Dentition,  75 
Dermis,  56 

Descent  of  man,  Darwin's,  129 
Destiny,  mankind,  165 
Development,  social,  form  of,  164 

early  prenatal  period,  42-45 

later  prenatal,  45-63 

postnatal,   63-70 
Differentiation,  and  extinction,  161 

relation  to  regeneration,  65 
Diprothomo,  10 

Discussion,  Age  of,  Bagehot,  145 
Drosophila,  155 
Dubois,  Dr.  E.,  13,  15 
Diissel,  Germany,  23 

Ear,  development,  48 

vestigial  muscles  of,  73 
Earthworm,  nervous  system,  85 
East  Anglia,  England,  36 
Ectoderm,  43 

derivatives  from,  43 
Education,  eugenical,  179 
Education,  Henry  Adams,  126 
Education,  importance  of,  181 

in  relation  to  mores,  142 
Effect,  cooperative,  165 


194 


INDEX 


EflFectors,  85 

sea-anemone,  89 
Egg  cells,  96,  158 

development,  42 

fertilization,  41,  42 

potency  of,  153 
Ehringsdorf,  Germany,  24 
Elements,  chemical,  freedom  of  action 
in  living  matter,  100 

chemical,  organized  in  nervous  pro- 
toplasm, 100 

of  animal  body,  99 
Embryo,   circulation,  change  at  birth, 
60 

condition,  at  birth,  61 

development  in  utero,  57 

prenatal  conditions,  60 
Embryonic  area,  43 
Emotion,  146 
Emotionalism,  163 
Emotions,  118 
Endocrine  organs,  49,  95 
Endoderm,  43 

derivatives  from,  43 
Environment  and  mutations,  156 
Environment,  diverse  of  man,  132 
Eoanthropus  daiusoni,  19-23 
Eolithic  period,  3 
Eoliths,  3 
Epidermis,  56 
Eugenics,  170 

importance  of,  181 
Eugenists,  148,  182 
Evolution,  and  natural  selection,  158 

and  progress,  127 

direction  of,  165 

causes  of,  153,  154 

cycles  in,  153 

directions  of,  159 

drama  of,  152 

germ-plasm,  157 

human,  tendencies  of,  179 

intellectual,  162 

main  lines  of,  161 


of  man,  155,  161,  162 

only  an  adjustment,  127 

neuromuscular  system,  92 

past,  causes  and  directions  of,  154- 

165 
progress  and  retrogression,  127 
progressive,  183 
reversal  of  principle,  166 
societal,  different  from  that  in  na- 
ture, 136 
Expedition,  American  Museum,  7,  12, 

37 
Experimentalists,  animal,  110 
Experimentation,  animal  difficulties  of, 

108-110 
Experimentation,  in  relation  to  varia- 
tions, 140 
Extremities,  phantasmal,  82 
Eye,  development,  48 
Eyelid,  vestigial,  72 

Face,  development  of,  56 
Factors,  Darwinian,  130 

individual,  154 
Female,  characteristics  of,  96 
Femur,  development,  55 
Fertilization,  41,  42 
Feudalism,  136 
Fishberg,  176 
Fisher,  Irving,  172 
Fishes,  spawning  instincts  of,  108 
Fitness,  animal,  135 

in  natural  selection,  158 

societal,  135 
Flints,  Foxhall,  36 

giant  of  Cromer,  36 

rostro-carinate,  36 
"Fluctuations,"  154 
Foramen,  ovale,  60 
Fore-brain,  45 
Forest  beds,  pre-Glacial,  19 
Fossil  man,  Africa,  11 

Asia,  12 

Broken  Hill  mine,  12 


INDEX 


195 


conditions  of  preservation,  7 

Cro-Magnon,  31-36 

Dallas,  Texas,  10 

Dawn  man,  19-23 

Heidelberg,  16-19 

Heidelberg,  age,  19 

intelligence  of,  114 

Lansing,  10 

Mousterian,  23 

Neandertal,  23-28 

Nebraska  loess,  10 

Piltdown,  19 

Piltdown,  age  of,  22 

pre-Mousterian,  35 

Rancho  La  Brea,  10 

record  of  discovery,  9 

South  American,  10 

Tertiary,  36 

Upper  Paleolithic,  31 

Upper  Pliocene,  36 

Vero,  Florida,   10 
Frank,  T.,  180 
Freedom  of  mind,  101 
Frog,  112 

intelligence  of.  111 
Frontal,  areas  of  brain,  120 

Galley  Hill  skull,  35 

Galton,  F.,  167,  169,  171 

Geikie,  19 

Genes,  154 

Genial  pit,  22 

Genital  organs,  external,  development 

of,  54 
Germ  cells,  157 

Germany,  champion  of  a  code,  142 
Germinal  cells,  union,  42 
Germinal  inheritance,  157 
Germ-plasm,   154,   158,   163,   164,   171, 
182 

environment  of,  156 

evolution  in,  157 
Gill  clefts,  49 
Girl,  growth  of,  67-69 


Gonads,  development,  53 

grafting,  71 

migration,  54 

producing   sex   cells   and   hormones, 
97 
Government,    a    cultural    adjustment, 

134 
Gower,  Wales,  31 
Graduates,  college,  children  of,  171 
Gravel  beds,  Hastings,  19 
Gravels,  Piltdown,  19 

Trenton,  10 
Greece,  decay  of,  179 
Gregory,  W.  K.,  14,  16,  19,  22 
Grimaldi,  34 

features  of,  34 

relation  to  Bushmen,  34 
Grotte  des  Enfants,  France,  34 
Ground  sloth,  11 
Growth,  63 

bone,  67 

curves  for  height  and  weight,  dl 

controlled  by  internal  secretions,  64 

decreasing  rate  of,  64 

hereditary  factor  in,  64 

period  of,  64 

relative  rate  of,  in  organs  of  body, 

retarded  by  certain  factors,  64 
Grypotherium,  11 

Guinea    pigs,    gonad    transplantation 
in,  96 

Habits,  fixed,  107 

Haeckel,  100 

Hair,  development,  56 

fetal,  56,  77 

regulation  of  development  by  hor- 
mones, 56 

slopes,  56 

tessellated  junctions  of,  56 
Haldane,  102 
Harelip,  57 
Heart,  auricles,  51 


196  INDEX 

development,  50 

ventricles,  51 
Height,  average  of,  69 
Helix,  of  ear,  73 
Hermaphroditism,  spurious,  53 
Hernia,  formation  of,  53 
Hind-brain,  45 
Homo  neandertalensis,  23-28 
Homo    {Paleanthropus)    heidelb  erg  en- 
sis,  16-19 
Homo  primigenius,  23-28 
Homo  rhodesiensis,  28-31 
Homo  sapiens,  18,  31-36,  40 

differentiation,  36 

Grimaldi  type,  34 
Hormones,  50,  96,  157 

eflFect  upon  personality,  95 

of  interstitial  cells,  97 

relation  to  nervous  system,  95 

see  Internal  secretion 
Horse,  evolution  of,  9,  64 
Hrdlicka,  A.,  10 
Human  intelligence,  114-122 
Human    race,   present   conditions   and 

tendencies,  165-179 
Humerus,     containing     supracondylar 
foramen,  77 

development,  55 
Humors,  95 

and  Hormones,  95 
Hunter,  J.,  experiment  of,  67 
Huxley,  T.  H.,  131,  156 
Hybrids,  176 
Hydrogen,  99,  101 
Hypophysis,  see  Pituitary  body 

Ideographs,  2 

Implements,  Eolithic,  19,  22 
Indian,  North  American,  116 
Indo-China,  amalgamation  in,  176 
Industries,  Magdalenian,  12 

pre-Crag,  36 

table  of,  4 
Inferences,  human,  121 


Inguinal  canal,  53 
Inheritance,  and  variation,  153-156 
social,  142,  157 

factors  and  mental  capacity,  171 

germinal,  157 
Instinct  and  reason,  105 
Instinctive,     actions,     theory     of     the 
origin  of,  107 

manipulations,  119 
Instincts,  106,  111 

animal,  108 

biological  utility  of,  106 

hereditary,  106 
Institutions,  human,  rise  of,  138 
Intellect,  development  of,  153 
Intellectual   power    and   cultural   sur- 
roundings, 116 
Intelligence,  122,  166 

and  consciousness,  112-114 

and  relation  to  nervous  system,  119 

animal,  104-112 

evolutionary  processes  of,  112 

frog.  111 

function  of  nervous  system,  104 

future  development  of,   122-125 

guinea  pig,  111 

human,  114-122 

individual,  field  of,  119 

prehistoric  man,  114 

primates.  111 

rudimentary  power  of,  112 

variation  in  human  races,  115 
Interest  and  emotion,  146 
Intermarriage,  170 

Internal     secretion,     development     of 
organs,  49 

influence  of  puberty,  69 

see  Hormones 
Interstitial  cells,  97 
Intestine,  appendix  of,  73,  74 

caecum  of,  73,  74 
Intussusception,  63 
Invention,  an  adjustment,  134 
Inventions,  great  progress  in,  164 


INDEX 


197 


Iron,  age  of,  2 
Irrationalism,  163 
"Ishmaels,"  168 

Isolation,  geographical,  lack  of,  175 
racial,  174 

Jacob's  cavern,  11 

Jaw,  Heidelberg  man,  16 

shrinkage  of,  75 
Jews,  amalgamation  of,  176 
"Jukes,"  168 

Kaa,  109 

"Kalikaks,"  168 

Keith,  Sir  A.,  10,  11,  18,  20,  22,  26,  28, 

30,  35,  36 
Krapina,  Austria,  24 
Kultur,  159 

Labor,  division  of,  a  mores,  137 
La  Chapelle-aux-Saints,  France,  24 
La  Ferrassie,  France,  24 
La  Naulette,  Belgium,  24 
La  Quina,  France,  24 
Language,  118 

a  mores,  137 

advantage  of,  to  man,  118 

as  a  mores,  141 

man's  control  over,  120 

responsible    for    man's    superiority, 
120 
Lanugo,  77 

League  of  Nations,  128 
Le  Moustier,  France,  24 
Life-conditions,  139 
Life  cycle,  70 
Lightfoot,  John,  1 
Limbs,  development,  55 

pentadactyl,  55 
Liver,  development,  50 
Lungs,  development,  49 

Magazine,  Natural  History,  11 


Male,  characteristics  of,  96 
Mammalia,  Pleistocene,  12 
Mammals,  instincts  of,  108 
Mammary  glands,  supernumerary,  77 
Man,  ability  to  accustom  to  different 
environments,  133 

American,  40 

and  anthropoids,  131 

behavior  of,  120 

bodily  evolution  of,  162 

Caucasian,  40 

controlling  his  evolution,  166 

dispersal  of,  6 

Ethiopian,  40 

evolution  of,  155 

fossil,  see  Fossil  man 

Java,  see  Pithecanthropus,  14 

Malay,  40 

Mongolian,  40 

Mongoloid,  11 

Neandertal,  14 

nervous  system  of,  84 

nervous  system,  summary  of  evolu- 
tion in,  102 

New  World,  11 

normal  life  cycle,  72 

phylogeny,  36 

Prehistoric,  species,   13 

Primitive,  language  of,  118 

progressive,  evolution  of,  161-165 

races  of,  38,  40 

similarity  of,  132 

structural  relations,  39 

structural  unit  of,  39 
Manipulations,   instinctive,    119 
Mankind,  birthplace  of,  5 
Mantle,  46 
Marriage,  136,  147 

a  cultural  adjustment,  134 

hindered  by  modern  conditions,  169 

productivity  of,  169 
Marshall,  Alfred,  178 
Mastodon,  engraving  of,  11 

remains  of,  11 


198  INDEX 

Mate  selection,  169 
Mating,  assortative,  169 
Mauer,  Germany,  16 

sands,  16,  17 
Maupas,  theory  of,  72 
McGregor,  J.  H.,  15,  18,  20 
Mechanism,  neuromuscular,  85 
"Melting  pot,"  177 

Roman  Empire,  180 
Mendelian  combinations,  154,  155,  170 

inheritance,  177 
Mendelism,  154 

Mental  life,  various  factors  which  in- 
fluence, 124 
Metazoa,  39 

MetchnikofI,  theory  of,  71 
Mexico,  racial  amalgamation  in,  176 
Mesoderm,  43 

derivatives  from,  43 
Mid-brain,  45 
Miller,  G.  S.,  Jr.,  20 
Minot,  on  diflFerentiation,  161 

theory  of,  72 
Moir,  J.  Reid,  22 
Momsen,  179 
Mores,  137,  138,  139 

and  education,  142 

and  imitation,  141 

and  life  conditions,  138 

and  sex,  138 

code  of  behavior,  147 

learned  not  inherited,  141 

transmitted  by  tradition,  141 
Morgan,  T.  H.,  155 
Morula,  42 

Mousterian  industries,  3,  4 
Mowgli,  109 
Mulattoes,  176 
Murals,  cavern,  12 
Muscle,  rectus,  76 

sternalis,  76 

subtegumentary,  76 
Muscles,  development,  53 

effectors,  85 


shifting  of  position,  55 

vestigial,  73 
Mutations,  154,  155 

and  environment,  156 

directions  of,  159 

their  causes,  156 
Myelin  sheath,  47 
Myotomes,  44 

"Nams,"  168 

Nasal  cavity,  development  of,  57 

Natural  law,  147 

Natural  sciences,  future  achievements 

in,  123 
Natural  selection,  135,  158,  178 

elimination  of  the  unfit,  143,  166 
Naturalists,  observations  of,  108-110 
Neandertal  man,  anatomical  features, 
24 

ideas  concerning,  28 

modern  representatives  of,  28 

skeleton,  23,  24 

skeleton  compared  with  Cro-Magnon 
man,  25 
Neolithic  period,  2 
Neopallium,  46,  93 
Nerve  cells,  46 

development,  49 

evolution,  49 

number  in  cortex,  93 

see  Neurones 
Nerves,  afferent,  48 

motor,  46 

myelin  sheath,  47 

sensory,  46 
Nervous  elements,  lacking  in  sponges, 

92 
Nervous    organization,    sea-anemones, 

86 
Nervous  system,  adjustors,  84,  86 

and  organization,  99 

and  personality,  81-83 

and  sex,  94-99  ' 


INDEX 


199 


central,  84,  86 

diffuse,  87 

earthworm,  85 

effect  of  interstitial  secretions,  98 

effectors,  85 

in  relation  to  intelligence,  104 

influenced  by  environment,  95 

intricate  structure  of,  84 

man  and  higher  animals,  84 

organization,  84 

receptors,  85 

reflex  mechanism,  47 

rudiment,  44 

summary  of  evolution  in  man,  102 

sympathetic,  85 

vertebrates,  93 
Neural  groove,  44 

tube,  44 
Neuromuscular  mechanism,  85 
Neuromuscular    system,    evolution    of, 

92 
Neurones,  46 

internuncial,   84 

motor  or  efferent,  84,  85 

see  Nerve  cells 

sensory  or  aflPerent,  84,  85 
New  Zealand,  mixed  races,  176 
Nitrogen,  99 
Nose,  development,   57 
Notochord,  44 
Nourishment  of  embryo,  prenatal,  57 

Obercassel,  Germany,  32 
Old  age,  see  Senescence 
Oldoway  ravine,  11 
Olfactory,  archipallium,  93 

cortex,  93 

organ,  development  of,  57 

organ,  retrogression  in,  73 

pits,  57 
Ontogeny,  52,  164 

course  of,  159 
Organicism,  102 
Organism,  structural  unit  of,  39 


Organization,  134 

and  a  society,  analogy  between,  129 
in  relation  to  nervous  system,  99-101 
nervous,  of  sea-anemones,  86 
sponges,  90-91 

Organs     of     body,     relative     rate     of 
growth,  66 

Orthogenesis,  156 

Osborn,  H.  F.,  4,  18,  34,  35,  36 

Ouse,  Sussex,  19 

Ovum,  fertilization,  41,  42 
structure,  42 

Pacific   Islands,    racial    amalgamation 

in,  176 
Paleolithic  period,  2 
Pallium,  46 
Pan  vetus,  21 
Pancreas,  development,  51 
Parables,  129 

Parathyroid  gland,  development,  49 
Parr,  Thomas,  70 
Particles,  protoplasmic,  152 
Pathways,  hereditary,  106 
Pearl,  R.,  174,  175,  178 
Pech  de  I'Aze,  France,  24 
Perception,  sense,  116 
Personality,  and  nervous  system,  81-83 

influence  of  sex  glands  upon,  98 
Phantasms,  145 
Phylogeny,  52,  164 

course  of,  159 

provisional,  of  man  and  anthropoids, 
36 
Pineville,  Missouri,  11 
Pithecanthropus  erectus,  12-16 
Pituitary  body,  development,  49 
Placenta,  development,  58 

filter  against  bacteria,  59 

intervillous  spaces,  58 

osmosis  in,  58 

passage  of  materials  through,  58-60 

separation    of    fetal    and    maternal 
blood,  58 


200 


INDEX 


villi,  58 
Pleistocene,  8,  10,  17,  22,  36 
Plica  semilunaris,  73 
Pliocene,  16 
Polydactylism,  55 
Pomace  fly,  155 
Population,  and  subsistence,  178 

effect,  of  the  world,  178 

foreign-born  birth-rate,  174 

limits  of,  178-179 

maximum,  178 

native  birth-rate,  174 

negro,  of  United  States,  176 

South  American  countries,  176 

United  States,  178 
Postnatal  retardation,  68 
Prepubertal   acceleration,  69 
Primary  germ  layers,  43 
Primates,  intelligence  of.  111 
Primitive  streak,  43 
Processes,  rational.  111 

selective,  143 
Products,  cultural,  134 
Progress  and  evolution,  127 

due   to   specialization   and   coopera- 
tion, 160 

definition  of,  159-160 

limits  of,  160-161 
Propagation,  by  selection,  170 
Proportions  of  body,  changes  in  during 

life,  65 
Protestantism,  144 
Protoplasm,  primeval,  152 
Protozoa,  39 
Puberty,  69 

influenced  by  internal  secretion,   69 
Pygmies,  5 

Race,  composite,  characteristics  of,  177 
differentiation    and     amalgamation, 

174-178 
mixtures,  175 

Race  suicide,  135 
Roman  Empire,  180 


Races,  blending  of,  176 

difference  in  intelligence,  115 

primary,  of  mankind,  176 
Racial  isolation,  174 
Rational,  conduct,  105 

processes.  111 
Reactions,   adaptive,    113 

animal,  acquiring  of,  121 

reflex,  106 

spontaneous,  107 

summary  of,  in  various  animals.  111 

tropistic,  113 
Realm,    societal,    elemental    forces   in, 

149 
Reason  and  instinct,  105 
Recapitulation,  Law  of,  52 
Receptors,  85 

sea-anemone,  89 
Recombinations,  154 
Reflex  actions,  106 

theory  of  the  origin  of,  107 
Regeneration,  in  amphibia,  65 

in  man,  65 

power  of,  65 
Rejuvenescence,  71 
Religion,  136,  147 

evolution  of,  123 
Reproductive  system,  development,  53 
Retardation,  postnatal,  68 
Retrogression,  73-75 
Rhodesia,  Broken  Hill  mine,  12 
Rhodesian  man,  28-31 

skull,  30 
Ribs,  variation  in  number,  75 
Roman  Empire,  race  suicide,  180 
Rome,  decay  of,  179 
Rubner,  72 
Rutot,  A.,  4 

Schoetensack,  Dr.  O.,  16,  19 
Science  and  religion,  144 
Sea-anemone,  creeping,  88 

effect  of  stimulation,  86 

effectors,  89 


INDEX 


201 


feeding  of,  87,  88 

nervous  organization,  86 

receptors,  89 

sense  organs,  90 

structure,  86 

tentacle,  effect  of  detaching,  87 
Secretions,    interstitial,   effect   on    ner- 
vous system,  98 
Segments,  44 
Segregation,  170 
Selection,  130,  143 

a  negative  process,  143 

ordinary,  improvement  by,  148 

essential  processes  of,  143 
Selenka,  Madame,  13 
Self-direction,  146 
Self-maintenance,  137 
Senescence,  70-72 

theories  of,  71 
Senile  degeneration,  see  Senescence 
Sensation,  82 
Sensations,  primitive,  101 
Sense  organs,  retrogressive  changes  in, 
73 

sea-anemone,  90 
Sense  perception,  116 
Sensorium  commune,  81 
Sex  and  nervous  system,  94-99 
Sex,  cause  of,  62 

center  of  society,  98 

conditions,  indifferent,  53 

definition  of,  95 

determination  before  birth,  62 

glands,  see  Gonads 

reversal   of,  by  gonad  transplanta- 
tion, 96 

transformation  of,  96 
Sextuplets,  62 

Sexual   characteristics,   determined   by 
gonad,  97 

primary,  96 

secondary,  96,  97 

secondary,  controlled  by  gonad,  97 


Shere  Khan,  109 
Skeleton,  cartilage,  55 

development,  55 

membrane,  55 
Skin,  development,  56 
Skull,  Calaveras,  9 

cap.  Pithecanthropus,  13,  14 

Gibraltar,  23 

pre-Neandertal,  18 
Slavery,  an  adjustment,  128 
Smith,  Elliot,  20 
"Social  theory,"  151 
Societal,  adjustment,  136 

code,  139 

evolution,  past  processes,  149 

fitness,  135 

range,  forces  at  work,  150 

realm,  149 

selection,  in  relation  to  war,  144 

selection,    various    forms    taken   by, 
145 
Societies,  struggle  of,  143 
Society,    and   organisms,    analogy   be- 
tween, 129 

human,  changes  in,  163 

relation  of  to  sex,  98 

stratification  of,   170 

systems,  cultural   adjustments,   134 
Sollas,  W.  J.,  12,  34 
Specialization,  and  progress,   160 

relation  to  regeneration,  65 
Spencer,  H.,  129 
Sperm  cells,  95 

in  fertilization,  42 

structure,  42 
Spider,  instincts  of,  108 
Sponges,  90-92 

lack  of  nervous  tissue,  92 
Spy,  Belgium,  23 
Steinach,  71,  97,  98 

gonad  transplantation,  96 
Stimulation,  effect  of,  in  sea-anemones, 
87 


202  INDEX 

Stone,  age  of,  2 
Sumner,  W.  G.,  137,  139 
Superstition,  163 
Supracondylar  foramen,  77 
Survival  of  the  fittest,  143 
Sympathetic  system,  85 

Tail,  in  man,  77 
Tariff,  protective,  128 
Tasmanians,  3 
Teeth,  cynodont,  14 

decay,  75 

dentine,  57 

development,   57 

enamel,  57 

first  set,  67 

fourth  molar,  7S 

Heidelberg  man,  18 

permanent,  67 

pulp,  57 

retrogressive  changes,  74 

taurodont,  14 
Tendency,  tropistic,  106 
Tentacle,  sea-anemone,  87 
Tests,  psychological,  American  Army, 

117 
Tetraprothomo,  10 
Thames  gravels,  35 
Thymus  glands,  development,  49 

fate  of,  50 

migration,  50 
Thyroid  glands,  development,  49 

migration,  50 
Tools,  not  used  by  lower  animals,  118 
"Trial  and  error,"  158 
Transmission,  of   mores  by  tradition, 

141 
Transplantation,  gonad,  96 
Trinil,  Java,  12,  13 
Tropisms,  105,  106 
Tubercle,  Darwin's,  of  ear,  73 

Urinary  system,  development  in  rela- 
tion to  genital  system,  53 


Uterus,  contractions  at  birth,  60 
digestion  of  wall  by  embryonic  cells, 
58 

Variation,  130,  139 

accidental,    in    relation    to    reflexes, 
107 

anatomical,  75-77 

and  experimentation,  140 

and  inheritance,  154-156 

and  the  world-code,  142 

depend  upon  verification,  140 

environmental,  154 

rational,  140 
Vas  deferens,  71 

Vascular  system,  development,  51 
Veins,  development,  53 
Ventricles,  51 

Vermiform  appendix,  73,  74 
Vertebral  column,  44 
Vestigial  structures,  72-75 
Villi,  of  placenta,  58 
"Vital  index,"  174 
Volition,  107 
Volitional  actions,  100 

War,  and  retrogressive  selection,  168 

form  of  societal  selection,  144 
V^ater,  101 

currents,  in  sponges,  91 

percentage,  in  body,  64 
Weight,  average,  69 

increase  in  prenatal  development,  63 
Weismann,  theory  of,  71 
West  Indies,  racial  amalgamation  in, 

176 
Woodward,  Smith,  20,  30 
World-code   and  variations,   142 

Yale  Babylonian  Collection,  2 
Yolk  sac,  43,  44 

"Zeros."  168 


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